Evil Me Scares Me

""Kill them all... no... no, that's not me... Help me! I'm scared of me...""

- Doc, Red vs. Blue

Maybe Bob saw an alternate timeline in which he was a Complete Monster. Or maybe he sees an evil goateed twin indulging in his dark fantasies. Or maybe he simply sees a sordid side to his character gaining ground. Or maybe he meets an evil future time travelling version of himself. Or maybe he delivers Extreme Melee Revenge to a Complete Monster, but has to be dragged away and only realizes afterward that he kicked him while he was down. Whatever the case, he is horrified. He may attempt to nip a Face Heel Turn in the bud (this may or may not backfire).

Anime & Manga

 * Vash the Stampede seems to feel shades of this, among other things, toward his Evil Twin, the Big Bad of the series. Especially in the manga, where their truly remarkable biology sets them apart more than in the anime and young Vash came a lot closer to going off the deep end, because Knives' Start of Darkness was a lot more justified.
 * In Inuyasha, Inuyasha is afraid of his full demon state, mainly because it could threaten the life of his Love Interest and puts humans in danger as well.
 * Similarily to the above example, Ichigo Kurosaki is afraid of his Inner Hollow taking over, as he transforms into an out-of-control but extremely powerful monster.

Fanfic

 * In the Harry Potter/Torchwood crossover, The Magic of Torchwood, de-aged Jack is frightened by his - admittedly distinctly unnerving- worst possible future self, portrayed by a boggart (it is explained in-universe that boggarts are very intelligent, it's just rare that a fear is strong enough for them to show it and take a sentient form) though Jack being Jack, he considers it to be good company.
 * Legend of Zelda Sacred Reliquary, Ganondorf of all people - the latest reincarnation regained his past lives' memories and regrets everything.
 * Inner Demons: Twilight Sparkle is horrified when she uncovers a prophecy that seems to foretell her becoming an Ultimate Evil and taking over Equestria. After discovering the prophecy, she's plagued by Bad Dreams about being consumed by her inner darkness, one of which opens with seeing herself proclaim her rule to the terrified citizens of Ponyville.

Film

 * We see a touch of this at the climax of Return of the Jedi, as Luke stops himself from finishing his Curb Stomp Battle against Darth Vader.
 * At one point in An American Carol, Michael Malone sees an alternate timeline where the South won the American Civil War, and he is a slaveholder who out-Legrees Simon Legree.

Literature
"I am the real Fitzgerald Michael Kreiner and I claim my five pounds. "
 * Rachel of the Animorphs goes through a process with results practically identical to Kirk in Star Trek the Original Series's "The Enemy Within" with a split into agressive and passive personality characteristics, each with their own flaws that get counterbalanced with the other strengths and with the passive side being frightened of the agressive violent tendencies of the other.
 * As the series goes on, Rachel (no longer split) gets more and more worried about her emerging Blood Knight tendencies. She could take comfort in the fact that her dark side unleashed was a Jerkass but not full-on Ax Crazy.
 * In the Doctor Who Eighth Doctor Adventures, future alternate Fitz, now known as Father Kreiner, scares Fitz. Being a Sad Clown Deadpan Snarker, he pretends not to take him seriously:


 * Commander Vimes in Discworld has The Beast. It's made clear in several of the books that the reason he's so devoted to the rule of law is horror as to what he might do without it.
 * In How to Live Safely In A Science Fictional Universe, Charles Yu says that peering into parallel universes, 35 of the other versions of himself (out of 39) were assholes. He mentions that if that many alternate versions of you are jerks, you're probably not hot stuff yourself.
 * In The Dresden Files, Bob the Skull's personality is heavily dependant on who has ownership of him at that time. With Harry, he's a sex obsessed, heavily snarky exposition centre. He is therefore terrified of what he was like when he was owned by the (now deceased) Complete Monster Necromancer Heinrich Kemmler, and has no interest in returning to that state of mind.

Live Action TV
""Bored now.""
 * In the Doctor Who story The Ultimate Foe, it turns out that the Valeyard was siphoned off the Doctor's twelfth regeneration. The Doctor is not happy.
 * Also in "Amy's Choice" the Dream Lord, the creepy villain of the episode is  Chillingly, the Doctor figures this out because, in his own words, nobody else hates him that badly (or thoroughly).
 * Willow in Buffy the Vampire Slayer. Although the thing that actually horrifies her is more the fact that she seems a bit... you know, gay. Turned right around when Willow decides to be a lesbian a few seasons in.
 * She's not horrified by the fact that Vampire Willow is "kinda gay," it's that Vampire Willow is into her.
 * She's also disturbed by the fact that Vampire Willow is so "skanky".
 * Later episodes seem to have Willow using call-backs to Evil!Willow's mannerisms, particularly when she goes on her Roaring Rampage of Revenge.


 * This is very much a running theme of the series. Faith is so disgusted with herself after she turned evil she wants to die. Buffy breaks down when she discovers how much like Faith she had become. Giles would very much like to keep the things he did as Ripper buried, thank you. Angel has that curse that makes him feel regret over the things he did as a Complete Monster. And part of the reason Spike hates Angelus is because of how much of a monster he made him.
 * One of Data from Star Trek the Next Generation's earliest encounters with emotion was feeling hatred when fighting the Borg. The fact that this first emotion of his was a negative one and that he apparently enjoyed indulging in the furious killing of an enemy disturbed him. Then we get his Evil Twin Lore turning up who embraces his negative emotions and so personifies them to Data (and is in fact the cause of Data's sudden unleashing of emotion). Data would probably have been scared of him, if fear hadn't been saved for a later episode.
 * Star Trek has a decent history of Evil Twins, what with transporter accidents and the Mirror Universe. There's the example of Kirk being a Literal Split Personality with an aggressive, hot headed side and a passive, weak-willed but logical side and the passive side is afraid of the aggressive one. Major Kira Nerys of Deep Space Nine gets a similar deal to Willow in the Buffy example.
 * However, since the Mirror Universe normally involves plots of being swapped with the guy on the other side (presumably to avoid having to deal with one actor being in a single scene) mostly you get the counterparts never meeting and at most Evil You Scares (but sexually intrigues) Me.
 * Or in Deep Space Nine's version, their opposite is usually dead on one side of the mirror or the other.
 * In Two and A Half Men, Alan worries in the episode "The Price of Healthy Gums Is Eternal Vigilance" that he may have unconsciously shoplifted a Silly Putty egg when he was nine, and has spent his life struggling to keep Bad Alan under control. He hasn't considered the alternative (true) explanation that.

Video Games

 * In the DLC chapters of Alan Wake, "The Signal" and "The Writer", Alan is stuck in the Dark Place as a result of the events of the main game, and has been split in two personalities, a rational and self-determined part, whom the player controls, and an insane and self-destructive part, who has gain control over the world and can shape it to his will. The former is at first very disturbed by the latter, but it later turns into downright annoyance as the Dark Alan keeps making up more and more absurd and contrived hindrances to slow his progress towards sanity.

Toys

 * In Bionicle, an alternate-universe Makuta Teridax who never turned against Mata Nui enters the main universe to confront the Big Bad who is just about on the verge of winning. It's not so much "Evil Me Scares Me" so much as "Evil Me Has To Die".

Western Animation

 * Happens repeatedly with several characters in Justice League after the titular heroes encounter their Well-Intentioned Extremist counterparts known as the Justice Lords.
 * Similiar thing happened in Justice League Crisis On Two Earths when they meet their completely evil counterparts.
 * In Avatar: The Last Airbender Aang actually says, "I was scary" when reflecting on the Avatar State. A little different since the Avatar State isn't evil but rather an implacable force of nature.
 * Danny Phantom's evil future ghost half, merged with his arch-nemesis' ghost half, Dan Phantom.
 * Family Guy: When Brian accuses Stewie of getting soft, Stewie decides to maximize his evil side. It backfires, kind of: he ends up creating a separate, wholly evil Stewie. He isn't happy once he see what the clone is capable of.