The bad route ofUndertale, most commonly referred to as theGenocide route, is the one in which the player actively attempts to clear the game in the most heinous manner possible; namely, by committing genocide on the race of monsters. It is not enough to simply kill every monster that happens to get in your way; you must actively hunt down every living monster in every region of the Underground, until random encounters no longer occur.

This route is also alternatively referred to as theNo Mercy route or theBad Time route, mainly by those people who are too squeamish to accept the true nature of the actions you must perform to accomplish this route.

• Addressing the Player: This trope is used to its fullest effect in the final segment of the Genocide route, drawing attention to the fact thatUndertale is a work of interactive fiction, not merely a static story.
  • First,Flowey describes his gradual descent into extreme antisocial behavior, in a way that eerily parallels how you ultimately succumbed to the temptation of trying the Genocide route, all while directly facing you and using your chosen name.
  • Next,Sans describes how the "anomaly" has been creating and terminating timelines willy-nilly, in what is clearly an in-universe description ofSave Scumming, before accusing you of being the one responsible. He too directly faces you as he explains all this.
  • And to cap it all off,after killing Flowey, an eerie child appears before you, bearing your chosen name. There's no interface, no other characters, no sound (save for an unsettling background noise); just a single overworld sprite on an empty black background, facing you directly. They explain in no uncertain terms that it wasyour human soul andyour determination that brought you to this point. It was your desire to max out your stats, your desire to push everything to its limit. You chose this path, and now it's high time to reap what you've sown.
• Alone with the Psycho: Toriel tries to keep you locked in the Ruins to protect you from the monsters outside. She realizes too late that she was really protecting themonsters fromyou.
• Arc Words:_{But nobody came.}
  • Once you have hunted down all available monsters in an area, the next time you get an encounter, you see only an empty battlefield, and those three words in tiny text.
• Being Evil Sucks: The Genocide route seems designed to make you feel this. It strips away the majority of the charm of the game, having much less in the way of puzzles and character interaction, in return offering only an endless slog of killing every enemy you encounter in only one or two hits, alongside many a self-inflictedPlayer Punch. The only thing it offers to compensate is the two toughest boss battles in the game.
• Beyond the Impossible: Undyne somehow taps into the power of Determination (which monsters aren't supposed to be able to do) to transform into Undyne the Undying.
• Bleak Level: Theentire game becomes progressively bleaker and bleaker on a Genocide run, and it's especially noticeable if you've done a less murderous run earlier. The point when it really begins to show is Snowdin Town; the normal run town is the most populated area in the game, but it's almost entirely abandoned in a Genocide run (apart from Monster Kid), and most of the flavor text has been changed to be much darker.
• Don't Make Me Destroy You: The final boss of the Genocide route takes this attitude with the player character once they first meet. The boss says "you are really not gonna like what happens next" if you fight them, trying to warn the human not to advance. When the human steps forward anyway, the boss gives a glorified shrug and starts the battle.
• Enfant Terrible: You, of course.The Fallen Child as well.
• Half the Man He Used To Be:
  • When Undyne takes a blow for the Monster Kid that visibly cuts her battle sprite in two, from shoulder to hip. Her upper half begins to slowly fall off... until she reforms herself for the real boss battle.
  • The final boss of the Genocide route has his torso diagonally slit in half all the way from his shoulder to his hip.
• Heroic Second Wind: In the Genocide route, Undyne takes a fatal blow to protect an innocent from the player. Before she dies, however, her determination triggers a transformation into the powerfulUndyne the Undying.
• He Who Fights Monsters: A major theme of the game and particularly this route. By continually fighting literal monsters, even to the point of excess, they start becoming actively afraid of you and your capacity for cruelty. Especially apropos because you are fighting creatures called "monsters", yet can possibly end up more horrific than almost anything you encounter if you so will it. It gets even lampshaded by both Sans very early and Asgore very late that the player character can't even be recognized as a human, meaning they visually change into a literal monster as well.
• If You're So Evil Eat This Kitten: In a meta sense, the game does this to theplayer if they're attempting a genocide run. Notably, you have to murder Papyrus in cold blood and attempt to kill the obviously defenseless Monster Kid.
• Infant Immortality: About two-thirds of the way through the route, you enter a very one-sided battle againstMonster Kid. If you insist on continuing your descent into depravity, you must take the opportunity to kill them.The trope is ultimately played straight because if you attack, Undyne swoops in to protect Monster Kid, and allows him to escape to safety.
• Moral Event Horizon: Despite gleefully murdering the downtrodden denizens of the Underground, and possibly even betraying the friendships you forged in other realities just to sate your sick sense of curiosity, there is ultimately only one Moral Event Horizon:the moment you kill Flowey, marking the point at which you have killed every monster that the game will allow. Cross this point, and the game will never allow you to redeem yourself.Even if you restore the world from nothingness, your save file is secretly corrupted; achieving a Pacifist ending after completing the Genocide route will yank your happy ending away from you at the last second.
  • The game makes it quite clear at several points on the Genocide route that you can always choose to stop killing. First, Papyrus blocks your way, and insists that you're a good person at heart; although when you kill him,hestill insists with his dying breath that there's still hope for you. Next is a monster that you cannot fight except in this route,Monster Kid; they stand their ground, trying to make you realize that you're not evil enough to be capable ofchild murder, though you can of course prove them wrong.

Finally, you come up againstSans the Skeleton, who opens up with a simple question: "Do you think even the worst person can change...? That everyone can be a good person, if they just try?" But by this point, you're too far gone, and you'll just ignore them as you menacingly advance toward your goal.Yes, even if you, the player, want to meditate on this question, your in-game character will automatically approach Sans without your input.

• Pre-Ass-Kicking One-Liner: "it's a beautiful day outside. birds are singing, flowers are blooming... on days like these, kids like you....S h o u l d b e b u r n i n g i n h e l l."
• Suspicious Videogame Generosity: In a Genocide run, killing Mettaton NEO results in enough EXP to jump from LV 15 to 19. You will most likely need the resulting HP boost for theFinal Boss.
• Wham! Episode: New Home has some extra reveals that shed light on the certain characters, firstthe chat with Flowey in the halls towards, that give you the full reveal of how he developed his wicked personality, and thenthe fight with Sans, where not only is he revealed as a case ofCrouching Moron, Hidden Badass, but he also reveals the full extent of hisknowledge about the resets and how it relates to hisSad Clown personality.
• What the Hell, Player?: As long as you're on this route, anything you do will elicit this sort of reaction. Even examining the potted plant in the MTT Resort Restaurant brings up the caption "(The potted plant is judging you for your sins.)".
• You Are Better Than You Think You Are: During a Genocide run, Papyrus will try to stave you off your destructive path by assuring you that you're a great person at heart and, if you just try, no matter how little effort you put into it, the great person you are will shine through. Should you kill him anyway despite his speech, he'll even use his last breath to promise you that he knows you can do better, even if you don't think so yourself. The amount of faith he puts in you has proven to be just as effective as Undyne's and Sans's beatdowns when it comes to making people abort their Genocide runs.
• Zero Effort Boss: Because this route requires you to grind excessively for EXP and LV, you quickly end up being overleveled for almost every boss fight, and murder is as easy as landing a single attack. The most extreme case isMettaton NEO; the game builds them up to be an intimidating foe, ready to rock your socks off. In actuality, they just stand around menacingly and don't even try to attack, making it impossible to lose against them.
  • Note that we saidalmost every boss; there are some highly notable exceptions.Specifically, one determined shark-lady and one nigh-untouchable skeleton.

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