Genocide Route

For one definition of the "No Mercy Route," where all encountered monsters are killed, see Neutral Route#Leaderless Ending.

Genocide Route
Sans warning the protagonist of a "bad time" on the Genocide Route
Mechanic type	Ending

if you keep going the way you are now...
...
you're gonna have a bad time.

Sans in Snowdin Forest

The Genocide Route leads to one of the three main endings of Undertale. It consists of the protagonist killing every possible monster in the Underground.

This route's ending can occur without prior completion of the game, unlike the True Pacifist. Once the protagonist completes the Genocide Route, subsequent True Pacifist Route and Genocide Route endings are altered – even after a True Reset, being informally called "soulless routes".

Method

Battle text after the protagonist exhausts the kill count.

The Genocide Route occurs when the protagonist kills every enemy (including mini, mid and main bosses) in every region: the Ruins, Snowdin Forest, Waterfall, and Hotland (the CORE is a sub-region of Hotland).

Starting in the Ruins, the protagonist repeatedly triggers encounters to kill all monsters. This is similar to level-grinding, which is earning experience points before progressing in other RPGs. After killing all monsters in an area, encounters still occur, but monsters do not appear. In a font size smaller than usual, the battle text reads "But nobody came.", which can also occur in a Neutral Route after killing all monsters in an area. This also changes the SAVE Point text to only state "Determination." instead of the usual lines.

After the small battle text message appears, the music for the area changes to a distorted ambient track, mus_toomuch.ogg. This track is a part of Your Best Friend playing at 1/13th speed (~0.077x or ~92% slower) with added reverb.

After exiting the Ruins, most overworld songs are lower pitch, slower versions of their Neutral and True Pacifist Route counterparts. Some NPCs no longer appear, and slight alterations occur in some locations, such as most puzzles already being solved.

If the protagonist stops meeting the requirements for a Genocide Route at any point, they revert to a Neutral Route where the unaltered soundtrack plays. NPCs still occur in the region where the protagonist aborted the Genocide Route.

Requirements

The first SAVE Point in Snowdin Forest displays the kill counter for the first time.

• Exhaust the random monster kill counter in every region. This requirement must be done before approaching the final encounter of that area.
  • Encounters become increasingly harder to find as the protagonist grinds out the kill counter for each area (except New Home, in which they are scripted).
  • The protagonist can spare any number of random encounters (Snowdrake and Lesser Dog are exceptions, as seen below). Sparing certain monsters allows the protagonist to avoid fighting particular monsters such as the high-defense Jerry. The protagonist can also spare certain monsters so that they can kill monsters that offer more EXP and GOLD, such as Glyde.
  • The following is a table of the number of random encounters only that the protagonist must kill as stated at SAVE Points in red text, followed by the final boss of the area.
    • Ruins: 20 kills (Toriel)
    • Snowdin: 16 kills (Papyrus)
    • Waterfall: 18 kills (Undyne the Undying)
    • Hotland/CORE: 40 kills (Mettaton NEO)
    • New Home: No kills (Sans; The protagonist automatically kills Asgore and Flowey upon confirming their respective dialogues.)
  • Snowdrake and Lesser Dog are unique in that Snowdrake must be killed before Snowdin's kill counter is exhausted and Lesser Dog must be killed if it is ever encountered. Both are also part of the kill counter. They are scripted to appear in at least one random encounter, but it is possible to avoid Lesser Dog's encounter by reaching Glyde's room and encountering it repeatedly instead.^{[citation needed]}
  • Once the protagonist satisfies the kill requirement, SAVE Points display the message "Determination."
• Kill every boss and miniboss (secret bosses So Sorry and Mad Mew Mew are not accessible, and Glyde is optional). All minibosses (excluding Napstablook, Snowdrake, and Lesser Dog and including Shyren) can be encountered even after the kill counter is exhausted, which can be used to obtain extra EXP.
  • Toriel
  • Snowdrake
  • Doggo
  • Lesser Dog (if it is ever encountered)
  • Dogi
  • Greater Dog
  • Papyrus
  • Shyren
  • Glad Dummy
  • Undyne the Undying (triggered by fighting Monster Kid)
  • Royal Guards
  • Muffet
  • Mettaton NEO

Kill counters for different areas have different requirements. If certain events are triggered before clearing an area completely of monsters, the protagonist is automatically sent back to the Neutral Route. For example, if Papyrus's battle is initiated without exhausting the Snowdin kill counter, the cutscene proceeds as if on the Neutral Route. Even if the protagonist is captured and then goes back to finish off the last monsters, re-fighting Papyrus still proceeds as on the Neutral Route. Once a Genocide Route is aborted, it cannot be returned to without reloading to a SAVE before it was aborted or resetting entirely.

There is a glitch if the protagonist enters the fight with Toriel. If there is still one possible encounter left in the Ruins, the fight with Toriel proceeds as normal for a Neutral route; however, if Toriel is killed, the protagonist continues a Genocide Route.

Differences

Ruins

After Exhausting Kill Counter

• If the protagonist exhausts the kill counter before encountering Napstablook, they vanish when the protagonist approaches them, skipping the fight with them.
• The NPCs for Froggit and Vegetoid do not appear.
• In Toriel's Home, checking the cupboard in the kitchen prompts the flavor text "Where are the knives.", instead of "Inside the cupboard are cookie cutters for gingerbread monsters."
• When checking the mirror, the flavor text, "It's me, <Name>." appears instead of "It's you!"
• When facing Toriel at the exit of the Ruins, the protagonist kills her with a single attack regardless of how well the attack is executed.
  • When attempting to talk to Toriel, the flavor text "Not worth talking to." appears, instead of "Ironically, talking does not seem like the solution to this situation."

After Killing Toriel

• In the next chamber, Flowey appears, even if he was killed on a previous Neutral Route, and identifies the protagonist as the first human.

Snowdin

Before Meeting Requirements

• On the Neutral Route, the lone snowball is usually described as, "(It looks like a snowball...) (Actually, it's a snowdecahedron.)" is instead "(It's a snowball.)" after the kill counter has been exhausted. On the Genocide Route, this message is displayed by default.
• When encountering Sans, he is disturbed by the fact the protagonist does not react to his joke. He then attempts to hide them behind the conveniently shaped lamp, but they ignore him. Papyrus runs in, and leaves after Sans tells him he found a human and does not notice the protagonist. Sans then tells the protagonist that they should continue "pretending" to be a human.
• The SAVE Points, instead of describing that the protagonist is "filled with determination", now start counting down how many monsters the protagonist has left to kill before the Genocide Route can progress (e.g. "16 left.").
• Snowdin Forest marks the first instance of overworld music being slowed down in the Genocide Route; Snowy is played at 0.4x instead of 0.95x speed. However, it is important to note that various events cause music in Snowdin to revert to its normal state (namely after the word search, tile puzzle, and bridge gauntlet segments); the music returning to its normal speed does not indicate a failure of the route.
• When Papyrus finally notices the protagonist, he initially does not recognize them as a human. The music slows down and becomes lower pitched when this happens.
• Doggo shivers when the protagonist approaches him.
• The protagonist can take three Snowman Pieces from the Snowman until they become a "useless pile of snow."
• The protagonist ignores all of Papyrus's puzzles, and some of them appear to be solved with Flowey's help.
  • The protagonist walks through the electricity maze before Papyrus finishes explaining it. The music speeds up and becomes higher pitched after this happens.
  • Sans and Papyrus have different dialogue regarding the word search when it is either checked or skipped.
    • If the word search is skipped, Sans remarks that he should have made the puzzle a Junior Jumble, as opposed to a crossword during a Neutral Route.
    • If the word search is checked, Papyrus complains that he "CAN'T WORK IN THIS ENVIRONMENT" before leaving.
  • The switch in the snow puzzle has already been pressed down by vines.
  • The spikes are already retracted for the X --> O puzzles, and Papyrus is absent.
  • The ice bridge for the ice X --> O puzzle is already expanded.
  • The protagonist cuts off Papyrus's explanation of the tile puzzle and walks through it before Papyrus can activate it.
  • The Gauntlet of Deadly Terror is retracted after Papyrus feels like the human would not appreciate it. After Papyrus leaves, Sans warns the protagonist that they will "have a bad time" if they continue the way they are currently going, specifically mentioning the protagonist's upcoming battle with Papyrus. He then seems to teleport out of the area, and the music stops.
• If the protagonist kills Greater Dog and has yet to kill Snowdrake, all the SAVE Points state, "That comedian..." until he is killed.
  • If Snowdrake is not killed before the kill counter is exhausted, the SAVE Point text changes to "The comedian got away. Failure." and the Genocide Route is aborted.

After Meeting Requirements

• Once the protagonist exhausts the kill counter, all Snowdin Town NPCs evacuate, except Monster Kid.
  • Shop is played at 0.2x instead of 0.925x speed.
  • Snowdin Town is played at 0.25x speed.
    • If mus_toomuch.ogg is triggered in Snowdin Forest, that music plays instead.
  • The protagonist can no longer sleep at the Inn.
  • Inspecting the Christmas tree at the center of town displays the message "Nothing for you."
  • Inspecting the unfinished book in the Snowdin Library yields the message "Some unfinished book."
  • The Innkeeper's Child is replaced with a decoy version.
  • Due to the absence of the Snowdin Shopkeeper, the protagonist can steal all of her wares and 758G from the counter. Inspecting the note on the counter displays the message "Please don't hurt my family."
  • Due to the absence of the Punk Hamster, the protagonist can climb onto the counter in Grillby's.

Papyrus confronting the protagonist

• The ball at the Ball Game disappears. Checking the hole says "There's a hole here." instead of "Ah! Wow! Woah! It's a "Hole"."
• Papyrus tries to convince the protagonist to be a good person and immediately offers to spare them. Even after being killed, he still believes that the protagonist can do better.
  • During Papyrus's confrontation, Bonetrousle plays at 0.2x speed.

Waterfall

Before Meeting Requirements

• On the Neutral Route, most of the Echo Flowers produce a message stating "It's strangely silent." after killing Undyne. On the Genocide Route, the flowers produce this message by default.

The smiley face appears when encountering a monster.

• Starting in Waterfall, encounters are marked by a smiley face above the protagonist's head as opposed to an exclamation point.
• Like Snowdin, most of the music is slowed down.
  • Waterfall is played at 0.13x speed.
  • Quiet Water is played at 0.5x instead of 0.9x speed.
  • Shop is played at 0.2x instead of 0.925x speed in Gerson's shop.
  • Temmie Village and Tem Shop are played at 0.5x speed.
  • Pathetic House is unaffected.
• All of the NPCs are absent, except Monster Kid, Gerson, and the Temmie Shopkeeper.
  • The Small Bird still appears on the opposite side of the gap when the protagonist enters from the left side, however it disappears after reaching the Garbage Dump.
• Due to the absence of the Ferry and the Small Bird, the protagonist cannot return to Snowdin or any earlier point in Waterfall until Undyne is defeated.
  • All the areas between the Ferry Dock and the Garbage Dump also become permanently inaccessible because of this, preventing the protagonist from getting the Ballet Shoes and the Dog Residue if they have not already.
• Like Snowdin, most of the puzzles are already completed.
  • Rocks are not falling down the waterfall in the rock puzzle room.
  • The Bridge Seeds are already aligned.
  • The northern wall in the Wishing Room is already open.
• Onionsan does not appear.
• When Monster Kid offers to help the protagonist reach the ledge, the protagonist climbs on to the Kid's shoulders roughly.
• The protagonist's actions upset the Mad Dummy so much that it causes them to become corporeal, turning them into the Glad Dummy. Since the protagonist helped the Mad Dummy become corporeal, they immediately offer to spare them. The dummy must be killed in order for the Genocide Route to progress.
• Neither Napstablook, nor the snails show up in Blook Acres, meaning that the game of Thundersnail cannot be played.
• The "Ghouliday", "Spookwave", and "Spooktune" CDs do not appear in Napstablook's home.
• Gerson remains in his shop, and sells his items as usual, albeit with different dialogue. He also appears to have some meta-knowledge, knowing that the protagonist cannot harm him as shopkeepers cannot be fought, and thus their threats mean nothing.
• Temmie Village is empty except for the Temmie Shopkeeper, who behaves normally, seemingly unaware of what is happening, and the Temmie that watches the protagonist from within the wall.
  • The Tem Shop has no option to pay for the shopkeeper's college education – this is replaced with the option to buy "Premiem" Temmie Flakes at a price of 1000G, making it impossible to obtain the Temmie Armor during the Genocide Route.
• If the kill counter is not yet exhausted for Waterfall, a dialogue box appears between the second and third Echo Flowers on the pathway to the bridge (room_water19), reading "Strongly felt <number> left. Shouldn't proceed yet."

After Meeting Requirements

• An additional, unnamed SAVE Point appears in the room before the bridge and disappears after the bridge sequence.
• On the bridge, Monster Kid approaches the protagonist, saying that Undyne told them the protagonist had done bad things and began to see the truth in her words. They try to fight the protagonist, but when the protagonist retaliates, Undyne jumps in and takes the fatal hit. Instead of dying, however, she recovers and becomes Undyne the Undying, who is significantly more difficult than the ordinary Undyne boss fight.
  • After being defeated, Undyne dies with a smile, aware that Alphys is evacuating the monsters ahead of the protagonist, and will tell Asgore to absorb the SOULs he has collected.
• After killing Undyne the Undying, the "Welcome to Snowdin Town" sign is removed, although its hitbox is still present.

Hotland and CORE

Before Meeting Requirements

• Alphys is absent in her lab. Instead, Mettaton acknowledges the protagonist's malice and flees.
  • The lights are already on.
  • The console that shows the protagonist says "It's me, <Name>." when interacted with.
  • Upon being inspected, the hole in the wall yields the message "It's just here to complete the look."
• Like Snowdin and Waterfall, most of the music is slowed down.
  • Ooo, Another Medium, Hotel, and CORE are all played at 0.5x speed.
  • Alphys does not play at all.
  • Dating Start! is played at 0.25x speed in Bratty and Catty's shop.
  • Shop is played at 0.4x instead of 0.7x speed in the MTT-Brand Burger Emporium.
  • CORE Approach is unaffected.
• Like Snowdin and Waterfall, most of the puzzles are deactivated.
  • Most of the lasers are off. The only exceptions are the first opposing ship puzzle to the left (as soon as the protagonist approaches the laser, it turns off automatically) and the three lasers on the conveyor belt on floor 3 (these lasers are still active even if the puzzle in that room has been solved in the Neutral Route).
  • The puzzles involving shooting the opposing ship are already solved.
• All NPCs are absent except the River Person.
• The Royal Guards are encountered much earlier, at the three steam vents before the entrance to Mettaton's cooking show set, and they attempt to avenge Undyne. They can both be killed in one hit.
  • Checking either of the Royal Guards during battle will read "I see two lovers staring over the edge of the cauldron of hell", if checked a second time, it continues "Do they both wish for death? That means their love will end in hell.".
• Mettaton's quiz show, cooking show, news report, and musical performance do not occur.
• The elevator in Hotland can access every floor except for R3 from the start. However, floors L1, L2, and R2 are cut off by force fields, preventing the protagonist from getting the Stained Apron and encountering So Sorry.
  • The force field that cuts off elevator L1 disappears after reaching elevator R3.
• Muffet does not show up for her bake sale. It is still possible to buy from the bake sale, but this does not prevent the fight with Muffet. Before she is fought, she does not consider the protagonist to be fit to eat but attempts to dispose of them regardless.
  • If mus_toomuch.ogg is triggered in Waterfall, that music plays in Muffet's bake sale even if the kill counter has not yet been exhausted. The reason for this may be because the track that plays at the bake sale in other routes is Quiet Water, a track that plays in many areas throughout Waterfall along with its eponymous track.
• The Muffet fight still takes place, though the protagonist can kill her in a single attack, so long as the attack is well-executed. If not killed immediately, she has unique dialogue referencing the Underground's evacuation.
  • She talks about how Alphys unsuccessfully attempted to get the spiders to evacuate.
  • The telegram she receives states that despite the protagonist being a hyper-violent murderer, they never harmed a spider since there are no other spider enemies.
• All MTT Resort NPCs other than Burgerpants are absent.
  • Due to the absences of Bratty and Catty, the protagonist can steal all of their wares, as well as 5G from their shop. A note can be found which reveals that Alphys came to evacuate them to someplace "super duper safe," but that Bratty and Catty wanted to use up their gel pens before leaving.
• Examining the plants in the MTT Resort reveals that "(The potted plant is judging you for your sins.)"
• A Dimensional Box appears in the lobby of the MTT Resort.
• The elevator in the CORE is functional from the start and can be used to bypass the rest of the CORE.
• The monsters that ambush the protagonist near the entrance to the CORE and before the second laser puzzle are absent, though the monsters that ambush the protagonist along the "warrior's path" are still present, even if the kill counter has already been exhausted.

After Meeting Requirements

• Once the Royal Guards and Muffet are killed and the kill counter has been exhausted, the route is now locked and can no longer be aborted.
• The Mettaton encounter at the end of the CORE becomes a face-off against Mettaton NEO. Mettaton dies in a single hit, and the protagonist's LOVE is set to 19 regardless of their LV beforehand. Encounters no longer occur in any region after this happens.

New Home

• Small Shock plays at 0.6x speed in the place of Undertale.
• A Dimensional Box appears in front of Asgore's Home and in the Last Corridor.
• The present box in Asgore's Home that otherwise contains the Worn Dagger now contains the Real Knife, and the text "About time." displays when equipping it.
• The present box in Asgore's Home that otherwise contains the Heart Locket now contains The Locket, and the text "Right where it belongs." displays when equipping it.
• Examining various objects throughout Asgore's Home yields unique descriptions.
  • Padlocks, first time, if no keys are used: "(He leaves them in the kitchen and the hallway.)"
  • Padlocks, otherwise: "(There are two keys.)"
  • Padlocks, while unlocking: "(I unlocked the chain.)"
  • Closet: "Our clothes."
  • Left bed: "My bed."
  • Right bed: "His bed."
  • Drawing of a Golden Flower: "My drawing."
  • Bookshelves / Asgore's closet: "Nothing useful."
  • Asgore's dresser: "Still has that sweater."
  • Photograph: "..."
  • Refrigerator: "No chocolate."
  • Kitchen note: "I've read this already."
  • Journal: "The entries are always the same."
  • Stovetop: "Stovetop."
  • Mirror: "It's me, <Name>."
  • Calendar: "(The date I came here.)"
• While walking through Asgore's Home, Flowey talks to the protagonist. His dialogue replaces the story of Asriel and the first human on the Neutral Route.

Flowey's dialogue in New Home. The lack of name in the bottom left is unedited.

• Unlike in other encounters and like the encounters in New Home in the Neutral Route, the fallen human's name does not appear during the dialogue encounters with Flowey.
  • He tells the protagonist about his life ever since he was a flower, his own ability to SAVE, and why the protagonist started killing.
  • He even seems to break the fourth wall and insult "those sickos that stand around and WATCH it happen" for not playing the Genocide Route themselves.
  • Flowey reiterates his "Kill or be killed" mentality, saying that he and the protagonist would not hesitate to kill each other if the need arises. However, Flowey finally realizes in horror that he is not above this, and that the protagonist would eventually kill him too if given the chance. After the protagonist appears to aggressively approach him, Flowey flees. The music changes to a slower, low pitched version of "Anticipation" when this event occurs.
• In the Last Corridor, Sans does not judge the protagonist but instead warns them that they will have a bad time should they step closer. When the protagonist ignores his warnings and continue to proceed, Sans puts up a difficult battle in an attempt to stop them from destroying the timeline.
  • Sans's death automatically sets the protagonist's LV to 20.
• Within the room with all of the coffins, the red coffin says "It's as comfortable as it looks."

Flowey begs for his life as the last enemy on the Genocide Route.

• Within the throne room, Asgore mentions having never seen a flower crying (referring to Flowey's attempts to warn Asgore of the protagonist). The protagonist then proceeds to attack Asgore, killing him in one hit (on the console versions, the borders around the game window are immediately disabled upon engaging Asgore). Flowey finishes Asgore off, and then, with his face and voice turning to Asriel's, he begs the protagonist not to kill him. This is the final point where the game can be reset without consequences, as pressing any of the action buttons causes the protagonist to kill Flowey in eight hits.

• Instead of leaving the black screen and returning to the Throne Room, Chara appears on the black screen. They begin speaking to someone, either the protagonist or the player directly, without a dialogue box. After their introduction, a high-pitched wailing sound and echoing heartbeats will play.
  • Chara explains that the protagonist's determination was the reason that the former came back, and that the player taught Chara the reason for their return, power, and gave them the means to gain it. It was the protagonist's SOUL and determination that allowed them to destroy everything so that they could achieve this goal. Chara then lists the various stats that the player increases throughout the game as the very feeling they have whenever they are increased. They offer to destroy the world so that the two of them can move on to another world. At this point, two prompts are given: "ERASE" or "DO NOT."
    • During this conversation, the player cannot use the ESC button.
    • If the player chooses "ERASE," Chara calls the player "a great partner" followed by hollow eyes and stating that Chara and the player will be together forever, resulting in the world's destruction.
    • Choosing "DO NOT" causes Chara to be seemingly surprised at the player's refusal, thinking that the player must have misunderstood them. Chara then asks the player "SINCE WHEN WERE YOU THE ONE IN CONTROL?" with hollow eyes, which then results in a jumpscare. Chara then approaches the screen with a horrifying facial expression while apparently laughing, emitting a horrible noise as the screen shakes while flashing red and black. The game's window also vibrates (in the Windows versions) during the jumpscare.
  • Following either option, a larger slash animation is seen followed by the screen shaking and filled with "9's," resulting in the world's destruction, and the game closes. In console versions of Undertale, the screen instead blacks out with nothing happening for 30 seconds until howling wind plays.

• The window name is absent after Flowey is killed. After the giant slash animation, the entire window of UNDERTALE (in the Windows versions) shakes violently side to side, implying that the attack was damaging the world itself. The game automatically reverts to Windowed mode during Chara's jumpscare and the numerous 9s.

Aborting

The Genocide Route is aborted if the protagonist either completes an area by sparing the boss or reaches certain points in the game without exhausting the kill counter. Future areas appear as though in a Neutral Route, but any previous areas remain affected by the Genocide Route attempt.

• If the Genocide Route is aborted at any point before reaching New Home, the SAVE Points stop displaying the kill counter and stop displaying "Determination" once it has been exhausted, even in areas that the protagonist exhausted the kill counter in before the route was aborted, and go back to what they usually display. Exceptions to this rule are as follows:
  • After sparing Toriel
  • After sparing Papyrus (the music in Snowdin Town remains unchanged from when the route was still in effect)
  • After sparing Glad Dummy (the SAVE Points still display the kill counter, the music is still slowed down, and encounters are still marked by a smiley face)
  • After killing Mettaton NEO without killing every monster in Hotland beforehand (similar to Glad Dummy, which means that the encounters that tell the story of Asriel and Chara are marked by a smiley face)
• If the Genocide Route is aborted by sparing Papyrus, the protagonist may only hang out with him as they cannot flirt with him during the battle. Sans is at his post in Waterfall, thanking the protagonist. Sans does not offer to take the protagonist to Grillby's, as Snowdin is already evacuated.
• If the Genocide Route is aborted after reaching Waterfall, encounters stop being marked by a smiley face and go back to being marked by an exclamation point.
• If the Genocide Route is aborted by sparing Monster Kid, the protagonist fights Undyne normally.
• There is a specific neutral ending that can only be reached by fighting Mettaton NEO without having killed every monster in Hotland/the CORE beforehand. Mettaton still dies in a single hit, though the damage he takes is significantly lower and does not set the protagonist's LOVE to 19. He tells the protagonist that they were "holding back", exploding after his speech. In the ending's phone call, Sans hands the phone to Alphys.
  • If the Genocide Route is aborted by sparing Muffet or the Royal Guards before facing Mettaton, the protagonist enters the Neutral Route. However, NPCs in Hotland still do not appear, including Muffet and the Royal Guards themselves after being spared. This also leads to Alphys's ending.
• If the Genocide Route is aborted and Flowey is spared, Flowey chastises the player for aborting the Genocide Route before asserting that they just wanted to see what peace was like before taking it all away.
  • If the player resets after leaving the Ruins and before the world's destruction, Flowey confronts the protagonist at the beginning of the Ruins and wonders why they had reset before telling them to do whatever they want.

If the protagonist has gone past the point of no return in the Genocide Route (killing the last monster in Hotland/the CORE before the Mettaton NEO fight), they can simply reset their game as long as they do not give an answer to the final question from Chara.

Post-Genocide Game

Chara speaks without a dialogue box in the void.

Upon relaunching the game, only a black screen with howling wind appears, and the game's window is unnamed. Inputs do nothing, and the player must wait ten minutes before Chara addresses them.

Chara reminds the player that they destroyed the world and then questions if the player thinks they are above consequences.

• If the player confirms by selecting "YES," Chara simply says, "Exactly."
• If the player selects "NO," Chara asks them, "Then what are you looking for?"

However, Chara also suggests that they could reach a compromise, and offers to restore the world in exchange for the protagonist's SOUL. If the player agrees to this exchange, the game closes and appears to load normally the next time it is opened, while the console versions immediately reset. If the player declines the offer, Chara leaves the player.Rebooting the game and waiting for another 10 minutes will cause Chara to reappear with the same offer.

Once the offer is accepted, the game closes. When re-opened, the game functions as if the player just installed the game, as a naming prompt is given, and even Flowey has no memory of previous playthroughs. All future True Pacifist and Genocide endings are altered, but Neutral Route endings remain unchanged. Routes completed after dealing with Chara are often referred to as "soulless" routes (i.e., "Soulless True Pacifist Route" and "Soulless Genocide Route"). The player fights Photoshop Flowey on the next Neutral Route.

Changes

The True Pacifist Route ending is noticeably altered.

• At the end of the Soulless True Pacifist Route, the following occurs:
  • If Frisk chooses to stay with Toriel, when the latter leaves a piece of pie before leaving the room, after four seconds they turn over in bed in the final scene and face the camera to reveal Chara with red eyes having taken full possession of Frisk. A lower-pitched version of Photoshop Flowey's laugh plays to accompany this reveal.
  • If Frisk says they "have places to go," the photograph of Frisk and friends shown in the final scene changes – Frisk is replaced with Chara, and the faces of all the other characters have been crossed out with a red X.
  • "The End" text changes from white (or yellow) to red, and the Annoying Dog does not show up to sleep under the text. The track Anticipation plays extremely slowly three seconds after the "THE END" text appears.
• At the end of another Genocide ending:
  • Chara calls themself "The demon that comes when people call its name." It does not matter when and where. Time after time, they will appear, and with the player's help, they will eradicate the enemy and become strong. Chara then lists the various stats that the player increases throughout the game as the very feeling they have whenever they are increased. Chara then comments that they and the player are not the same, stating that the protagonist's SOUL has twisted feelings they no longer understand. Chara then wonders why the player continues to recreate the world, and why they continue to destroy it. Chara then states that the player is wracked with a "perverted sentimentality." Chara then suggests that should they recreate the world once again, a different course of action would be advised.
  • If the player selects "DO NOT" this time, Chara points out that this very feeling is what they had been talking about. Chara then comments to the player that unfortunately, regarding their choice, "YOU MADE YOUR CHOICE LONG AGO." This causes another jumpscare, and once again closes the game.
  • As Chara already has the protagonist's SOUL and is fully aware of the events before, any future Genocide endings will also reuse the same dialogue, and instead of making another offer, the world is automatically reset regardless of the choice made.
  • In the console versions, after the world is destroyed again, the game does not close, and instead the screen blacks out for about 30 seconds before the regular title screen plays again.

Consequence Avoidance

The first two sub-sections only apply to the computer versions and the third only applies to the console versions.

Save Locations

Default save locations are as follows:

• Windows:
  • Windows XP: %SystemDrive%/Documents and Settings/%USERNAME%/Local Settings/Application Data/UNDERTALE
  • Windows Vista and later: %LOCALAPPDATA%/UNDERTALE
• Linux:
  • DRM-free (old versions): ~/.config/UNDERTALE_linux
  • Steam(old versions): ~/.config/UNDERTALE_linux_steamver
  • 1.02 and newer: ~/.config/UNDERTALE
• Mac: ~/Library/Application Support/com.tobyfox.undertale/

Modifying/Deleting Files

To return to a playable state, the player can enter their save data folder and either:

• Delete the last directory in the aforementioned save location for the player's respective system; this removes everything the player has done in the game as if it is being played for the first time.
• Delete or rename the files system_information_962 and system_information_963 in the aforementioned save location. This removes any effects of having done the Genocide Route. The system_information_962 file is created after erasing the world, and system_information_963 is created after the player gives their SOUL to Chara.
• Uninstall the game and do a fresh reinstall.

GOG players using GOG Galaxy may need to disable cloud saving before carrying out any of these steps. Also, these methods are not sufficient for players of the Steam version, as the Steam Cloud backs up the acquisition of the system_information_962 and restores it if deleted (even if cloud synchronization is disabled). Players of the Steam version have to wait 10 minutes and accept the offer, changing system_information_962 to system_information_963. This deletes system_information_962 from Steam Cloud and does not upload anything. Players can delete system_information_963 in the save location later. There is also a way to render the system_information files unreadable by Undertale by modifying their security settings under file properties to deny read permission.

Console versions

In the console versions, the consequences of the Genocide Route can be removed if the player simply deletes the Undertale save data from the console's storage.

Demo

After completing a Genocide playthrough in the Undertale Demo, the ending screen appears with red text that reads "That was fun. Let's finish the job." replacing the credits while playing Anticipation at a very slow speed. Also, all the pages of the manual but the first and last are replaced with said ending screen, and the last page is replaced with a picture of a faceless Flowey.

The faceless Flowey image.

The ending screen.

Trivia

• The Ruins is the only area that does not have a slowed down song (except in Toriel's Home), nor solved puzzles, as it is the first area of the game and no criteria for the Genocide Route are met until the kill counter for the Ruins is exhausted.
• Papyrus is the only character in the game to continue to believe the protagonist can "do better" and redeem themself for the greater good after the genocide of Snowdin and dying to the protagonist.
  • He is also the only main character in the game that does not attack the protagonist despite the latter committing genocide and Papyrus attacking the protagonist on the Neutral Route.
• If the Genocide Route is aborted by sparing Muffet or the Royal Guards after the kill counter for Hotland has already been exhausted, Mettaton NEO still sets the protagonist's LV to 19 as if they are still on a Genocide Route.
• Since Mettaton NEO lacks attacks in his battle, and Alphys does not encounter the protagonist during this route, Yellow Mode is not used, making it impossible to be seen during this route. This is shared with the Nintendo Switch exclusive SOUL Mode of Mad Mew Mew.
• Before Undyne dies on the Genocide Route, she states that Alphys had told Asgore to absorb the six human SOULs, but when the protagonist encounters Asgore, he has not.
  • Evident by Asgore's lack of urgency at the end of the route, it is possible any message sent to him warning of the human was intercepted.
• In version 1.00, the Snowdin SAVE Point message, "That comedian...," appeared even if Snowdrake was already killed. According to Toby Fox, the message appearing so often was a bug and was fixed in version 1.001.
• The Royal Guard check dialogue is a direct reference to the Japanese novel "Kitchen" by Banana Yoshimoto.
• Sans's last words in the Genocide Route include "don't say i didn't warn you," possibly indicating he knew what would happen at the end of the route.