Super-Powered Evil Side



"But I'm not my "kind", not anymore — your shadow leeches saw to that. I'm half Toa of Light, half Toa of Shadow. This was what you wanted, wasn't it? Toa consumed by darkness, Toa not hampered by things like mercy or morality. Well, now you can choke on it."

- Toa Takanuva, Bionicle

The fight's not going so well for our hero. He's wounded and at the end of his strength, and his barely scratched opponent looks down at him and sneers. And then the hero somehow suddenly taps into a massive hidden power source within him and unleashes a can of whoopass on his opponent.

It's not exactly the hero any more, though. He's got glowing eyes, some new Facial Markings, different way of talking, some new threads, and a lot less compunction about ripping someone in half. It's his Super-Powered Evil Side. Think of it as the Enemy Within when it's not the enemy, or as Jekyll and super-Hyde.

Interestingly, the name notwithstanding, this character isn't necessarily evil- they just seem like it because a superpowerful version of a normal person who has no compunctions about destroying things randomly objectively registers as "evil" on most people's scale. To be technically accurate, this is more of a Superpowered Alter Id—this personality is the physical manifestation of the character's basic drives, without having to deal with the inconvenience of higher thought process and morality. Although sometimes, this character will actually have traits of actually being evil or even worse.

Similarly, this character isn't necessarily super powered either. Often times the liberation from morality make it so the character can go all out. He doesn't need to pull his punches since he's not concerned about killing his opponent, and thus much more of a threat.

Keep in mind, of course, that once the Id is out of the subconscious it's not likely to want to go back in. Thus, the hero faces the very real threat of not returning to normal. Generally speaking, though, he's usually safe unless he starts thinking Evil Feels Good.

The narrative purpose of having a super-powered evil side is that it provides a way of saving a hero who is otherwise beaten, but without making the hero look disproportionately powerful. It answers the question "why don't they just do that all the time?" with "because then the evil would take over." Additionally, if it leads to a Face Heel Turn, it can serve the same purpose as Good Is Dumb in reverse—it justifies taking one member of the Five-Man Band or whatever, and making them a match for their entire team while they've given in to evil.

The converse of With Great Power Comes Great Insanity, since in this case, with great insanity comes great power.

One possible variation on this trope makes the Evil Side the original personality. This creates the odd situation of an "Evil" super-powerful monster whose "Good" not-as-powerful personality is dominant for whatever reason.

This can sometimes cross over with Beware the Nice Ones and can get into Nightmare Fuel territory. Compare with Crouching Moron, Hidden Badass, Jekyll and Hyde and One-Winged Angel. Frequently overlaps with Sealed Evil in a Can and Sealed Badass in a Can. Contrast Heroic Resolve, My Name Is Inigo Montoya, and Helpless Good Side, although that last one sometimes goes hand in hand with this. May be caused by The Corruption. One possible way of Taking A Level In Badass, and in many ways, this is what The Berserker does.

Sub-Trope of Enemy Within and Super-Powered Alter Ego

Anime and Manga
"Yusuke: For what I desire is ending the world and everyone in it. For I am AHAHAHAHAHAHAHAHAHA... psych!! Damn, you guys are gullible!"
 * In Magical Project S Misao is normally a shy, physically weak and powerless girl, but when she transforms into her evil side, Pixy Misa, she becomes super confident and super competent. At full power she is able to easily defeat the heroine Sasami.
 * Himura Kenshin from Rurouni Kenshin is a technical pacifist in battle, fights with a reverse-blade sword and vowed years ago to never kill again. But if things seem to be getting out of hand even for him to handle (usually when his friends are in danger), his fighting style and mindset slowly begin changing into the highly pragmatic and ruthless Battousai, the assassin he was ten years ago. He switches the extremely humble sessha for the brash ore, loses the de gozaru from his speech, his eyes turn gold and more slanted and he moves for the kill. In the anime, Battousai seems to be considered an actual personality Kenshin has learned to seal off by creating his rurouni persona - he has to literally punch himself in the face to push it back and revert back. In the manga, this gets lampshaded a bit when Kenshin remarks that his face muscles have cramped and he isn't able to end his permanent death glare.
 * Not exactly superpowered. Just going all out, full power, without fear of hurting nor killing his foe.
 * Son Goku of Dragon Ball faced this early on with his Oozaru transformations. In this form he loses all sense of self while gaining immense strength and size; the best solutions found were to either cut of his tail or blow up the moon. The transformation into the Oozaru, while generally a bad thing, did have two positive outcomes. One was the escape of Goku and friends from Emperor Pilaf; the second was Gohan defeating Vegeta... by landing on him.
 * Moving on to Dragonball Z, the Super Saiyan state acts like this without proper training. The transformation occurs in a moment of pure rage, and the resulting personality shift leaves the Saiyan struggling with an overwhelming anger. This is likely a major reason why the first recorded Super Saiyan destroyed the world he was on: He couldn't gain control of himself and so destroyed everything around him.
 * Frieza even comments on this when Goku beats him around as a Super Saiyan. He asks if Goku isn't being as cold blooded as he is, and concludes that Goku is still struggling to control the rage in him and that it's uncertain if he will win. Then again, by the time of the Cell saga, Goku has no trouble switching his power on and off without any bad effects.
 * Goku stated that while in the Hyberbolic Time Chamber, he and Gohan trained to act normal even when in Super Saiyan form. This may be why he can switch back and forth without any personality change. It should also be noted that the Super Saiyan forms are suppose to make the person more attuned to their Saiyan nature (the heartless, ruthless, Blood Knight). As such, Goku finds himself unable to use the Spirit Bomb while in Super Saiyan form. Even after mastering it, the state still taints his pure heart while he's in it.
 * Son Gohan during the Cell Games is a chilling example in anime. It is more than a little disquieting to watch the kind-hearted and sensitive little boy we have come to care about turn into a gleefully cold-blooded sadist when he achieves the Messianic power of Super Saiyan 2.
 * Gohan's Mystic Power-Up in the Buu saga is even more this, it is all the rage, anger and ruthlessness of his Saiyan heritage without the actually transforming into a Super Saiyan, in fact in this form he is supposedly more powerful than a Super Saiyan 3.
 * Vegeta seems to regain some of his old nastiness whenever he fights as a Super Saiyan (against the androids first, then later against second-stage Cell). Even Son Goku loses his usually unbreakable self-control the first time he achieves Super Saiyan while fighting Freeza, though he seems to partially regain it by the end of the battle.
 * Ichigo in Bleach is the embodiment of this trope. He becomes much stronger when his inner hollow is allowed to come out, or comes out on its own accord. The inner hollow is a completely different personality, behaving differently and mocking Ichigo about his weakness even as he attacks their common enemy. Ichigo gains half a hollow mask, yellow eyes, and the ability to block sword strikes with his bare hands. His sword's energy blasts become black and can be guided to the target. The best part about this form is that it is truly opposite: he is always smiling, as opposed to Ichigo who is (almost) always frowning, he tells jokes, he's the complete opposite of Ichigo. The first time he uses this form in combat is during his final battle with Byakuya Kuchiki, an Aloof Older Brother, in the Soul Society arc. Sure enough, Byakuya doesn't do much more than widen his eyes a bit.
 * Later on, Ichigo This wasn't achieved without a climactic Battle in the Center of the Mind, however. Twice, even.
 * And now we're back to square one regarding exactly where his evil side is, since (major spoiler of the past two manga arcs)
 * Inu-Yasha's demon side in Inuyasha, although it could also be interpreted as With Great Power Comes Great Insanity, as his bouts of insanity stem from having too much demonic power for his half-human body to handle. His Empathic Weapon Tessaiga acts as a Restraining Bolt.
 * Subverted in that eventually Tessaiga itself is so powerful that his demon side is actually weaker by comparison.
 * Suikotsu of the Shichinintai is a doctor with Split Personality whose darker side is a sadistic, blood-thirsty murderer.
 * In Naruto, most of the Tailed Beasts that are sealed within people are Superpowered Evil Sides, except for Shuukaku, which is more of a Superpowered Drunk Off Its Ass Side for The Stoic Woobie Gaara, and the Eight-Tailed Beast, which Killer Bee seems to be able to force to submit through sheer awesome. Despite their massive power, all can be suppressed in some way.
 * Sasuke and the curse mark. During the Chunin Exams arc, Orochimaru gave him a curse mark, which, once activated, turned the quiet, elite loner into a sadist who broke a guys arms without a second thought. Creepy! "You seem quite attached to these arms of yours."
 * Everyone with the curse mark, but especially the one with the original curse mark, Bi-polar Juugo.
 * Susano'o becomes this for Sasuke. Karin began noting his chakra becoming colder and darker when he was close to achieving it...and when he did...it basically was a giant demon that formed around him.
 * In Hellsing, Seras Victoria's berserker mode could be counted as her Super-Powered Evil Side.
 * Lucy from Elfen Lied is a variant of this trope - while she was originally the 'true' personality, she suffered a nasty head wound that caused Split Personality and left her nonpowered good side, Cute Mute Nyuu, in control. The times when her 'true' self resurfaces fits this trope to a tee.
 * In the manga, we learn that
 * Orson from Record of Lodoss War is literally a Berserker Class and, when he gets angry, he becomes an unstoppable killing machine that wields a massive claymore as if it were a toothpick.
 * Sumire's Anti-Virus mode (called "Berserker") in Venus Versus Virus.
 * Vash the Stampede's eponymous weapon in Trigun is triggered involuntarily by such events.
 * There is less 'evil' here than 'Evil Twin pulled the trigger' or occasionally 'moment of Unstoppable Rage.' Vash has never shown a superpowered evil side, although he does have the related tropes of Crouching Moron, Hidden Badass, an Evil Twin, and the occasional burst of aforesaid temper, after he witnesses a massacre or something else heinous.
 * Yugi's powerful alter ego in Yu-Gi-Oh!, Yami Yugi, is not actually evil, but he is a lot less concerned for the well-being of his enemies. Yami Bakura and Yami Marik, on the other hand, are both gleefully, psychotically evil. (Regular Marik isn't exactly a nice guy either.) In the manga, however, Yami IS evil, at least initially. Word of God stated in a Shonen Jump Q&A that Yami Yugi actually WAS evil at first, due to a few millennia of his soul being imprisoned, but that his experiences with Yugi and his friends gradually helped him regain his sense of righteousness. The plot point was revisited in the second anime in the "Waking the Dragons" arc. After Yugi's soul gets imprisoned, leaving Yami in control 24/7, he starts to regress back to his original evil nature, without Yugi's kind nature there to temper his drive for vengeance. Which makes him a more vulnerable target to Dartz's machinations.
 * Dark Yugi seemed more like he was giving evildoers poetic justice for messing with Yugi and his friends rather than doing it for his own evil delights in the initial chapters of the manga. And while he looked pretty scary while doing so, that doesn't mean he was evil. He's more of a superpowered evil side that isn't actually "evil". I'd like to see this interview myself to see if this came directly from the author or the editors of the American Shonen Jump (Word of God matters more if it comes from the former). Also, his rage and desperate desire to win during the "Waking the Dragons" filler saga isn't anything like his calm and collected confidence in the original manga.
 * Let's see. Sets man on fire for real, sends explosive vial sliding across the makeshift air hockey table (which goes boom on the loser, and it may or may not have been real), inflicting post traumatic stress disorder on Kaiba by turning him into a card (and inspiring him to be much more evil)... Yeah, Yami was evil. The only thing that made it acceptable is because every victim very definitely had it coming. That, and every shadow game he ran was a fair test of character.
 * Judai, Fubuki, and Kaiser in Yu-Gi-Oh! GX... except Kaiser doesn't gain an evil side as much a new evil persona.
 * Displayed in Yu-Gi-Oh! 5D's with the Dark Signers. Aki, too.
 * The eponymous warriors of Claymore constantly run the risk of becoming "Awakened Ones" when using their powers. In that state, they become their superpowered evil sides without any chance of turning back to their original forms.
 * The twist is.
 * Quiet and retiring Haru's alter ego, "Black Haru," from Fruits Basket is a humorous take on the trope. In the anime (or early in the manga), at least. It's played for some serious drama later in the manga.
 * Along the same vein, that goes for the brief 'cameo' of in the later chapters as well.
 * When Yuuri from Kyo Kara Maoh reaches an appropriate level of moral outrage, he involuntarily transforms into a larger version of himself with cooler hair, amazing magical powers and a thirst for justice.
 * ...who almost always says he's going to kill people, even though he 'dislikes bloodshed', but has no confirmed kills, and is usually confirmed as not having hurt anyone. Once he sentenced an Unlucky Childhood Friend and her quarry to go on a date. Another time he mistook an assassination attempt for an earthquake and saved everybody, even the enemy soldiers who'd been trying to kill him. Also, he has been known to say nonsensical things about fire brigades etc., just like Yuuri always does, just in a serious, booming way.
 * In the manga he gets a lot closer to the 'evil' line, but is a lot less divorced, in terms of identity, from normal Yuuri, whose lifelong tendency to a really violent temper is underlined. But the manga is darker than the anime. And Yuuri accidentally stabbed Wolfram half to death a while back in the novels. Genre Woobiefication?
 * When Kazuma of Kaze no Stigma taps into his evil side (really a reversion to his old behavior in his backstory), he will do whatever it takes to accomplish his goals, no matter who he has to hurt (or mind crush!).
 * In JoJo's Bizarre Adventure part 5, the protagonist Giorno Giovanna develops a new stand "Golden Experience Requiem" which is intelligent and can act on its own, and completely destroys his enemy Diavolo, causing him to experience death over and over again for all eternity.
 * Ginji's Raitei persona in GetBackers. also has one, when  The same way Ginji is the "Thunder Emperor," he's "the Prince of Terror."
 * In Daa! Daa! Daa!, you can see a crystal-clear example in Christine, the older Hanakomachi... when a girl (human, alien, it doesn't matter) approaches his beloved Kanata in a remotely romantic way, she emits a black aura and her eyes glow: it's your cue to get the hell away. In such state she is capable of feats like lifting trees & breaking concrete walls. She's not evil, just clingy.
 * Subverted in Samurai Deeper Kyo: prior to his further training under his master Muramasa, Onime no Kyo was in fact weaker than Mibu Kyoshiro, who was merely feigning weakness to complete the facade of a harmless medicine peddler.
 * Moka's "super-vampire" side in Rosario + Vampire. Super-Vampire Moka speaks to her normal self through her Power Limiter, giving her guidance that she needs. This one isn't evil so much as very emotionally cold, though.
 * Though recent chapters have revealed that Inner Moka is the true personality of the one body and the Outer Moka was created
 * Tsukune's ghoul transformation is much closer to the trope. He requires a power limiter like Moka to keep it under control, but unlike Moka, he's pretty much a complete monster without it.
 * As of Chapter 41 it seems he's at great risk of becoming
 * In Heroic Age, the giant mech-like warriors of the Heroic Tribe, called the Nodos, can eventually let out a Superpowered Evil Side when two fight together - whether against each other, or side by side - called Mental Chaos, when they enter a pure blind berserker rage. Considering a single Nodos can sometimes destroy a whole planet on its own at its normal levels of power, a Nodos in Mental Chaos is a frightening thing indeed. In Bellcross, the Nodos that serves the human Age, Mental Chaos is shown by his skin and "armor" turning dark gray, almost black, and a set of blue spheres implanted in his body begins to glow bright red. And he roars a lot.
 * Guts, the protagonist of Berserk, is known to slip into this state during particularly tense moments.
 * In the h-anime Makai Tenshi Jibril (Translated title: Jiburiru - The Devil Angel), Meganekko-with-a-crush Meimi is given the sadistic Magical Girl persona of Misty May, the "Devil" counterpart to the heroine Rika, (St. Jibril/Jiburiru)
 * Closer to the trope definition would be Rika's evil form in the sequel, or Hikari's Black Aries form in the third game.
 * This happened in Guyver once, but it was a doozy.
 * Though this wasn't so much the Guyver being evil, as obeying its Prime Directive of wearer-preservation.
 * In D.Gray-man, Allen's Innocence seems to have a mind of its own and tends to upgrade itself when Allen gets particularly angry or emotional. It also can control Allen when he's unconscious, and it tends to be very vicious. Then again, it's only dangerous to Akuma.
 * Also Arystar Krory, although he has less of a Super-Powered Evil Side than a Superpowered Deadpan Snarker Badass Side.
 * There's also the Noah, although they're (affably) evil to begin with.
 * Well, Tyki Mikk comes in black and white, but I don't think Noah consciousnesses change, except in that one stabby incident. 'Tyki Mikk, now in black, white, and Roiling Chaos. White out of stock.'
 * Allen, with the Fourteenth Noah  The Fourteenth hasn't been seen in actual combat yet, so 'superpowered' may still in question (yeah, right), but  definitely hints at the evil part.
 * In the most recent chapters, there are clear hints that the Fourteenth is terrifyingly powerful, even by Noah standards. Remember,.
 * Son Goku from Saiyuki. His 'evil side', the Seiten Taisei, is akin to a heretical chaos god and nearly overthrew the Heavens, goes on an Unstoppable Rage whenever unleashed, and usually ends up trashing both the enemy, AND his teammates by the time he's finally stopped. The only thing that keeps him in check is the crown he wears which serves as a Restraining Bolt.
 * The normally timid Cho Hakkai's demon form, which leaves only puddles of blood and entrails where his enemies once stood.
 * Actually Hakkai is in complete control while his limiters are off. Even as a human he was a bit of a ruthless bastard.
 * In Soul Eater:
 * is infected by some of Medusa's black blood, which manifests itself as a devil living inside his head offering him power in return for giving in to the insanity. On the one occasion give into it in order to stand a chance against The Dragon, the trope is almost fulfilled to a tee... Except it's not so much a 'superpowered evil side' as a 'Nigh Invulnerable giggling lunatic side who catches The Dragon completely off-guard'.
 * While not anywhere as drastic a change as the above, Stein's tactic against Medusa, of giving into his own madness, could also be seen as this. Though this side is not so much 'hidden' as it is what Stein would be if he didn't hold himself back through fear. He also seems able to control it frighteningly well, if Spirit's comments at the time are anything to go by.
 * Koyori in Nurse Witch Komugi has a literal evil Magical Girl Split Personality that she is completely unaware of.
 * Lina from Slayers when she's
 * IIRC, Word of God says that
 * The "berserker spirits" aka The Dragons from Ikki Tousen. So far, we have four dragon holders: Hakufu, Ryuubi, Sousou, and
 * Sonic X: Absorbing the negative energy of an entire factory's worth of fake Chaos Emeralds coupled with seeing his friends tortured unleashed Dark Sonic for the first time in animated continuity. Complete with white eyes and navy-dark energy all over his body, plus the ability to tear anything that pisses him off to shreds.
 * The main character of 666 Satan is actually the container of Satan himself along with nine other demons that have the ability to possess people. There are also ten angels, none of which are evil or attempting to take over but some are incredibly vain and judgmental.
 * While not necessarily "evil," a mechanical version of this can be found within Gundam Wing, specifically in the form of the Zero System, a computer system in the Wing Zero which interfaces with the pilot's brain, enhancing his reaction time and aggressiveness, and allowing him to process tactical data with superhuman speed and efficiency... with a fun little side effect of driving the pilot temporarily Ax Crazy. Given that they're still inside a giant, city-killing death machine with all their piloting skills boosted, results are predictably messy.
 * It should be noted that the Zero System can be used safely: the pilot must keep a clear head and not be conflicted in his thoughts towards the battle. In this case the pilot then gains all the benefits without the insanity. Both Heero and Zechs reach this point in the end - and, in fact, Heero eventually becomes so relaxed about the obligatory in-cockpit Mind Rape that he starts offering it to his fellow pilots as therapy. Astonishingly, it works.
 * Mobile Suit Gundam 00 also has fun with this - Allelujah Haptism has a Split Personality: Hallelujiah, a blood-thirsty "warrior" half whom is more skilled than just about any other pilot in Celestial Being.
 * Then subverted with
 * Then there's the Unicorn Gundam. Normally a high performance mobile suit with generally above average statistics but nothing of any particularly remarkable quality, when the pilot and it come into contact with a Newtype enemy and the pilot feels a strong enough emotional pull (usually anger), the Gundam feeds off of it and transforms into the eponymous Unicorn Gundam, now in its "NT-D" (Newtype Destroyer) Mode. Its speed ramps up significantly, its strength seems to increase, it gains new abilities related to its psycoframe, and worst of all the suit's AI will stop at nothing short of a manual override or a Heroic RROD to kill any Newtype in weapon range. This is entirely not good for anyone who happens to be facing the thing down, as it generally goes from on an even footing or slightly underperforming the enemy to stomping their face in on a one-sided epic beating.
 * Dark Schneider/Lucien in Bastard!!. Tiny, fifteen year old boy turns into the infamous eponymous bastard, the all-powerful Exploding Wizard. Then subverted since Darsh does a lot of dorky things outside of battle and seems much more like a Jerk with a Heart of Gold than anything else, with some people often remarking that compared to the Dark Schneider of fifteen years ago, this one is practically a saint.
 * In Saikano, Chise's personality while in the Ultimate Weapon form could be psychotically vindictive, threatening on multiple occasions to utterly eradicate anyone who got in her way or made her mad, be it friend or foe... and that she could do so with ridiculous ease made her even more horrifying.
 * Parodied in Yu Yu Hakusho. Yusuke He then decides to have a little fun at the expense of some alarmist commandos who wanted to take him out.
 * Parodied in Yu Yu Hakusho. Yusuke He then decides to have a little fun at the expense of some alarmist commandos who wanted to take him out.

"Maya: What the... It's ego border has completely vanished! Impossible to analyze! Ritsuko: Eva, free of it's confinement by human, is returning to it's original form. Absorbing human and Angel, it's becoming a being close to God. Heaven, earth and all creation in a giant swirl of complementation. All to please the wishes of one man... and for just that reason... a new life transcending reason has come. With the cost of eradicating all life previously known... Misato: Just like what happened 15 years ago... Ritsuko: That's right. To continue with Second Impact, . This is the end of the world."
 * Late in his fight with Sensui,
 * Sensui himself is an inversion of this trope. Of
 * Kurama displays a variant on this trope in the Dark Tournament when
 * Mayo Kagura from Mai-HiME Destiny. In a series where everyone has psychic powers, it's hard to stand out when you have boring ol' telekinesis... unless you have a Super-Powered Evil Side that can uproot trees and use them as weapons.
 * Ryo Takatsuki from Project ARMS. His right arm is a nanite-based entity known as the Jabberwock. Get him ticked off enough, and the Jabberwock spreads over and takes control of his entire body. Though more really, really angry rather than outright evil, this doesn't stop Jabberwock from doing such feats as
 * In Omamori Himari, It's explicitly stated that in this situation, they will be exterminated.
 * As of recent events in Mahou Sensei Negima, it seems that
 * Played with in that when he learns that, rather than decide he'll figure out a way to seal it away permanently, he instantly, without hesitation, decides to get the whole   over with right now and get it out of the way.
 * Technically
 * More like a Superpowered Dark Is Not Evil Side, really.
 * Urd of Ah! My Goddess (at least in the anime).
 * Pikachu in the Pokémon anime practically turned into a demon when he was
 * In Air Gear one of the strongest members of the protagonist's team has a split personality. Although Agito isn't exactly evil, his aggressive, bloodthirsty behaviour and great skill at the series' title sport make him this to Akito, one of the gentlest characters in the series. Additionally,
 * Change 123 demonstrates why, in the real world, this is less of a cool new power and more of a deadly serious problem; you don't want your high-school girlfriend to snap and try to kill someone on your behalf because they said nasty things about you...
 * The anime movie Tekkon Kinkreet has the main character Black get saved
 * Digimon has a few examples of this:
 * In Adventure, Taichi tries to force Agumon to evolve to perfect, causing the creation of SkullGreymon.
 * Digimon Tamers has Megidramon formed when Takato watches Leomon die.
 * In Digimon Savers, Marcus' emotion get the better of him, too, forcing ShineGreymon to enter ruin mode.
 * Digimon Xros Wars has two examples- DarkVolumon for  and the Whisper virus for.
 * Surprisingly enough, Shoutmon averted this by having no "evil" powered side.
 * Neon Genesis Evangelion introduced us to the concept of forty meter tall mechas going berserk. Let's take a tally, shall we?
 * Unit 00 during an activation test, it attempts to kill Gendo before starting to repeatly headbutt the wall until it runs out of power.
 * Unit 01 during the Sachiel battle, ended with an Unflinching Walk.
 * Not really berserk but the dummy plugs do battles the messy way. Just look at Unit 01's Rei-plug tearing Unit 03/Bardiel to pieces or the MP Evas' Kaworu-plugs literally gutting Asuka in End of Evangelion.
 * Unit 01 again during the Zeruel battle. It behaves more like a rabid gorilla than a human. Once it eats Zeruel's S2 Engine, it just stands there and roars to the sky.
 * The Rebuild 2.0 version of that battle turned out to be a Crowning Moment of Awesome as Unit 01 Mind Raped Zeruel to death while Shinji was in control the whole time. Keeping with the heavy symbolism of NGE, Unit 01 even manifested a halo about halfway through the Curb Stomp Battle. And we didn't even mention what happened afterwards...
 * The Rebuild 2.0 version of that battle turned out to be a Crowning Moment of Awesome as Unit 01 Mind Raped Zeruel to death while Shinji was in control the whole time. Keeping with the heavy symbolism of NGE, Unit 01 even manifested a halo about halfway through the Curb Stomp Battle. And we didn't even mention what happened afterwards...

"Mari: Let me show you the power of Eva purged of it's humanity. Mode change, code: THE BEAST! (Eva Fins blow off, teal cylinders emerge from the Eva, both pilot and Eva double over in pain) Endure this, Unit 02... for I will endure with you. Purged of humanity... there's nothing WE CAN'T DO!!!"
 * Mari hijacks Unit 02 during the Rebuild 2.0 Zeruel battle. Hoo boy, if you thought berserk is bad, you are in for a real shock. Even if an Eva goes berserk, it has restraints. Now you see what happens if you remove those: it behaves like a rabid xenomorph, snarling, salivating and making impossibly cool leaps.


 * In Violinist of Hameln, Hamel's  gives him a Super-Powered Evil Side that, however, is not usually activated by rage or being near death, as it usually the case, but instead takes over whenever he cannot carry on anymore and is close to Heroic BSOD. It comes with demonic physical changes, such as horns and wings, is powerful enough to easily devastate whole cities, indiscriminately murderous and completely uncontrollable
 * Tohma in Magical Records Lyrical Nanoha Force has his Black Knight form. When it comes out, he gains a Healing Factor, powerful magic, and is capable of performing a Zero Effect, which greatly drains the energies of anyone and anything in a wide area. Unfortunately, he loses over half his consciousness in this form, replacing it with an insatiable need to kill.
 * In D.N.Angel, Satoshi has  living in his head. Daisuke has Dark   living in HIS head, although Dark's more mischievous than evil.
 * I'd like to enter into the record Krad's fandom nickname: Homicidal Blonde.
 * Brain from Fairy Tail has Zero,
 * Hotaru Tomoe from Sailor Moon who has two other sides. Sailor Saturn and Mistress 9, who nearly destroyed the world.
 * Also Chibi-usa, who has one as well when she was brainwashed by the Wiseman known as the Black Lady.
 * This short cartoon about an anthro clione, whose SES is based on his real-life counterpart's mouth. The sequel stars a female version with a dash of Tsundere.
 * When Yaiba lose control of the Raijin Sword he turns in a lightning-blasting, destructive avatar of the God of Thunder.
 * In the series To Aru Majutsu no Index, the main character Touma, was shown to have an actual sentient being inside of him that appeared after having his arm cut off. The guy who who cut of said arm had a Oh Crap, moment when he realised that his power paled in comparison even though he reached the point of being higher than god. (This is a given because Touma's last name Kamijou can be translated several ways, on being "Invisible Demon".)
 * One Piece has Chopper, a shapeshifter who normally has three forms available. When he eats a Rumble Ball, he gets access to four more forms for three minutes. If he eats another before the cooldown wears off, he gets three more minutes, but the shapeshifting is uncontrollable. If he eats a third, he morphs into a giant monster that's incredibly powerful, incredibly resilient, and absolutely uncontrollable. In its first appearance, he just about one-shotted an enemy who had been beating him handily a moment before, then smashed through a castle wall and went on a rampage, destroying a dozen rooms before Franky managed to throw him into the ocean.
 * As with Chapter 645.
 * Piss off the softspoken, easygoing and always smiling Wolfgang Grimmer, from Naoki Urasawa 's "Monster", and you'll have to deal with "The Magnificent Steiner". Carnage ensues - though it's never directly shown.
 * The main character of Ikki Tousen, Sonsaku Hakufu is a token Idiot Hero with enough fighting skill to beat the crap out of a school attended only by martial artists and assorted thugs. But sometimes the enemy is just above her level and she founds herself beaten almost to death: vision blur, strenght fades... Congratulations! You've awakened "the power of the dragon" and the last thing you are likely to see is her raptured expression, while she strangles you to death or is going to stab you with a sword.
 * To be honest, pretty much everyone possessed by a dragon soul behaves this way... even if not a fighter.
 * Akira Fudou and Amon from Devilman may be the oldest example in the history of manga. And also an Unbuilt Trope, as the manga shows that having one wouldn't just conviently let you send it out on enemy too strong for you to take - taking Amon's powers changes Akira from meek and gentle boy into complete Blood Knight and that even without letting Amon out. Amon however only breaks free in an Spin-Off manga AMON and OVA of the same title. In anime Amon is a Complete Monster who   and in manga he is maybye just a bitter Anti-Hero, but still destroys several countries, just by passing through them.
 * Trinity Blood: Father Abel Nightroad only looks like a bumbling idiot most of the time—in reality, he's an extremely powerful and extremely dangerous Crusnik, a super-vampire that preys on regular vampires. He voluntarily limits his power to 80% activated, at most, though, although he does suffer from Sanity Slippage at that point.
 * Kagura, the adorable, profane, sukonbu-chewing, nose-picking heroine from Gintama goes from this to this when the self-imposed chains on her Yato blood get broken. She stops fighting to win and instead fights to kill with a savagery that scares her.
 * The protagonist of The Three Eyed One, Hosuke Sharaku, is a tiny, wimpy, Charlie Brown-esque boy who turns into an immensely powerful, larger, psychic supervillain when the bandage on his forehead is removed, revealing his third eye.
 * Double-subverted (at least) in Super Taboo with Yuu turning into "Instinct Yuu," which is less Omnicidal Maniac and more the personification of All Girls Want Bad Boys that's initially desired by his mother and sister since that side awakens whenever he's sexually aroused (minus everyone being drunk on Christmas) and implied to be inherited from his father, whose voice is even mesmerizing enough for Up To Eleven Phone Sex with his wife. Other than the confusing blackouts and reactions to sleeping with various women it/he's harmless until by being too rough with his sister, requiring a Battle in the Center of the Mind where Reason and Instinct (previously just a running gag where Instinct curbstomps Reason in cartoon-form ex. Barney-like dragon eating a knight) are personified as a Betty and Veronica that he has to choose between despite Evil Is Sexy. He finally chooses to be with Reason and rewarded with one last shot at his mom as himself (who's somehow a virgin) before being more steady with his sister as a happily ever after.

Comic Books

 * In the Alan Moore Retelling of the comic Marvelman, Miracleman, Kid Miracleman is the only survivor of a nuclear blast (He thinks) and stays in his superpowered form for years. In this form, but using his civilian name of Johnny Bates, he grows up. His moral code begins to erode because he is the most powerful man on earth and he has no one to tell him what to do. When Miracleman confronts him years later, he is the CEO of a computer company and a rather nasty piece of work. They fight, and he is forced to change back into a normal human child (His other self didn't age for years while in stasis) and left at an orphanage. There he is constantly bullied by other orphans, having to carry the dreadful knowledge that he could become more powerful than any of them, but he dare not because KM would start killing people. Then he is pinned one day, and some of the boys attempt to gang rape him, and this pushes him past the breaking point. The resulting awakening of KM results in the slaughter of the boys and a significant number of the population of London. Miracleman is forced to make him transform back into a human and end his life with a Neck Snap.
 * In an apocryphal story called "The Rascal Prince", a book read by followers of Johnny Bates who think he was a tragic victim tells a tale two ways: The revisionist version that depicts KM's meeting with an older woman as a flirty chaste romance, and as the Real Life version depicting a brutal rape of an unwilling victim.
 * Though not portrayed this way in the original comics, all subsequent portrayals of the Venom symbiote from Spider Man have made it out to be this, with even the comic book symbiote having been RetConned into a more malevolent entity.
 * The Incredible Hulk is the canonical super-Hyde. The Hulk, over time, has been softened down from "evil" to "pure id". Not that that stops him from racking up the damage bill every time he shows up.
 * Banner does have the Devil Hulk personality inside him, which is pure evil.
 * As well as Gray Hulk and Guilt Hulk—though Grey Hulk isn't really "evil"; he's another closer to "id".
 * Bruce Banner's wife Betty Brant has been transformed into the villainous Harpy. She's currently Red She-Hulk, who's more The Atoner.
 * Inverted by the Hulk of Marvel 2099 who is much more heroic than his human form.
 * X-Men:
 * Wolverine has a tendency to lapse into a "berserker rage" while in close combat. In this state he lashes out with the intensity and aggression of a mindless animal and is even more resistant to psionic attack. Though he loathes it, he acknowledges that it has saved his life countless times.
 * It's still not clear whether Dark Phoenix is Jean Grey's Super-Powered Evil Side or a variation on Grand Theft Me. (Whether Jean actually became Phoenix (and then Dark Phoenix) or was merely replaced by the Phoenix Force is in an almost constant state of Retcon, so the confusion is quite understandable.)
 * The New Mutants Magik, way back when, was partially transformed into a demon by Belasco. Her "Darkchylde" side is intelligent but malicious, though almost powerless on Earth, where her magic doesn't work very well. In the end it took over her and nearly ended the world in a major Crossover Event.
 * Legion from the same series was first introduced with a Super-Powered Evil Side in Jack Wayne, as well as a Superpowered Jerkass Side (the pyrotic Cyndi). He usually has one or more evil personalities, except when they are temporarily merged.
 * J'onn J'onzz, the Martian Manhunter, has a fear of fire for good reason. When he loses his fear of fire? He unleashes Fernus, the last Burning Martian who beat the entire Justice League of America at once and Batman needed to call Plastic Man in to help.
 * Yes. That Plastic Man.
 * Super Sonic in the British Sonic the Comic comic series. In that comic's canon, the Chaos Emeralds are full of pure evil (as energy), rather than their neutral alignment as confirmed as canon by Sonic Adventure. Super Sonic came about by overexposure to the Chaos Emeralds, and as such... he's totally insane, and totally evil. Not to mention sadistic, psychopathic... and equipped with the power of the Chaos Emeralds. When he split from Sonic and lost his powers he mellowed out, but returned to form when he got them back. The Archie comics did a homage to this in one issue, although in that canon there's generally no personality difference between Sonic and Super Sonic.
 * The Sentry and the Void, from Marvel Comics, are this trope taken to its extreme. They manifested as alter-egos of a single person, representing the good and dark sides of humanity, respectively. The Sentry is a superhero and the Void is a supervillain, and in a slight variation on this trope, the Void is exactly has powerful as the Sentry, and sometimes kills someone for every person the Sentry saves. They've also split into separate bodies, and sometimes make out with each other.
 * ONE TIME. And immediately following this, the Sentry Given the Void's speech prior to this, this doesn't decrease the Foe Yay any, though.
 * It was later revealed that
 * It was then revealed that the Void . The Sentry is kind of a mess.
 * Rising Stars:
 * Stephanie Maas/Critical Maas; The only normal in a town full of superheroes actually just shunted her super powers (including flight, strength, and creepy-puppetmaster mind control) into her secondary, psychopath personality.
 * Incidentally, Critical Maas is undoubtedly the inspiration for Heroes' Jessica/Niki, right down to and her penchant for calling her 'weaker' half 'little mouse'.
 * Jackie Estacado in The Darkness also fits this, and even likes it during the early parts of the series, as it gives him more unique ways to kill people.
 * Spider-Man:
 * Mr. Negative, a new Spider-Man villain, takes this to a whole new level  Both fight with each other in an interesting way - Negative likes to corrupt all   good deeds, while   helps people that suffer because of Negative.
 * Curt Connors and Lizard are often potrayed this way
 * Batman:
 * In the Batman RIP storyline, Dr Hurt's mental attacks on Batman unleash a "back-up personality" Bruce had installed in his psyche, known as the "Batman of Zur-En-Arrh", who is essentially Batman without Bruce Wayne, i.e. completely unstoppable, but willing to do things the normal Batman wouldn't dream of to get results (including, it is implied, torture). Once again, more of a "superpowered" (he's still a Badass Normal) Id Anti-Hero side than truly evil.
 * Two-Face is sometimes treated this way, being able to do the nasty deeds that "good" Harvey Dent can't bring himself to. This is particularly evident in the story "Two of a Kind".
 * Eclipso has acted as this to various characters in the DC universe. Subverted in one Blue Beetle comic, where Eclipso invokes this by releasing Jaime's darkest fantasy of ultimate power to serve as her champion against Paco. This backfires when
 * Raven of the Titans has to maintain strict control over her emotions to the point of being The Stoic. If she doesn't, she runs the risk of manifesting the extradimensional demon side of her family tree and becoming Daddy's Little Villain. This is one of the major reasons Raven and Beast Boy have never been able to make a relationship work in the long run despite strong mutual feelings for each other.
 * The Golden Age version of the Cheetah, Wonder Woman villain, was the violent split personality of a celebrity, Priscilla Rich.
 * Star Sapphire, villain and Love Interest of Green Lantern Hal Jordan, was similar, with Carol Ferris being unaware of what her alter ago was up to.

Fan Works

 * In the Pony POV Series, Princess Luna nearly reverts back into her Nightmare Moon form as a last ditch attempt to stop Discord, but manages to snap out of it.
 * Luna explains the Super-Powered Evil Side thing a bit in "AJ's Dream".
 * In he Mega Crossover fancomic Roommates Goblin King Jareth has one
 * In he Mega Crossover fancomic Roommates Goblin King Jareth has one

Film

 * Nathan Wallace in Repo! The Genetic Opera is a sweet, loving, family man. Until he puts on his helmet, at which point he becomes the merciless Repo Man.
 * Heavy Metal segment "Captain Sternn". While under the influence of the Loc-Nar, Hanover Fiste grows into a mightily muscled hulk and smashes through all opposition in an attempt to murder Sternn.
 * The version of Venom in the third Spider-Man movie is, of course, Peter's superpowered evil side, and it begins to affect his personality. The catch is, Venom's just enhancing Peter's latent personality traits, so out-of-costume his evil side comes across as a massive dork, and he is generally an asshole to everyone rather than being a figure of terrible power. Now for Brock, who's already portrayed as an asshole from the beginning, it's an entirely different story.
 * In The Iron Giant the giant is pretty powerful on his own, but friendly. You do NOT want to push his Berserk Button however.
 * In Forbidden Planet, the ancient alien civilization made a giant machine which is capable of turning thoughts into reality. It turns out that the machine works even better with subconscious thoughts.
 * Donning The Mask unleashes person's Superpowered Chaotic Side.
 * In the comics, however, it unleashes a more "evil" side to a person, as the eponymous mask takes the driver's seat of their mind.
 * How Luke defeats Vader in Return of the Jedi. Palpatine even says it: "Your hate has made you powerful." Per Word of God, this is how Anakin defeats Count Dooku ... but it has the cost of causing him to edge closer to The Dark Side.

Literature

 * Most incarnations of Jekyll and Hyde in popular culture portray Hyde as inhumanly large and strong, often ape-like. (For instance, the movie Van Helsing, The League of Extraordinary Gentlemen, etc.) In the original book, there is nothing superhuman about Hyde; he simply gives free rein to his base instincts. In fact, it is explicitly stated that Hyde is smaller than Jekyll, as Hyde is the primal and egotistical side of Jekyll. In the second volume of League, Hyde acknowledges this, but explains that the longer he's given free rein, and the more impotent Jekyll (the "good side") feels, the more powerful he becomes.
 * In Redwall, some animals (usually badgers) have an attack/split personality called the "Bloodwrath" which makes them extremely powerful, very resistant to pain... and also no longer able to tell friend from foe, meaning it's dangerous to anyone who's nearby when they go into this rage.
 * Oh god...the badger's gone berserk...RUN!
 * It Makes Sense In Context. They're going into berserker rages around smaller Funny Animals whose best option is to run - whether the badger is an enemy or one's commander.
 * Actually, it's not so much that they're resistant as that they can't tell they're hurt until they wake up.
 * In House of Leaves, Johnny Truant channels his Super-Powered Evil Side against Gdansk Man. The way in which Truant thrashes him and how the book describes Gdansk Man's wounds afterwards has led to some Epileptic Trees, such as.
 * Most werewolves that aren't villainous in human form get a lot more powerful and don't mind the taste of blood when transformed. Both the Kitty Norville and Mercy Thompson series have werewolf choosing their animal form for combat, and the Kitty Norville series portrays the Wolf as an alternate personality. The Wolf won't go out of its way to Kick the Dog, but it won't really care about taboos regarding cannibalism or murder.
 * '"Star Wars'': Exar Kun, Darth Vader, Ulic Qel-Droma, Darth Malak... when a Jedi falls to the Dark Side, it's time to get the hell out of Dodge.
 * , in Darren Shan's demonata series..
 * Havenite secret agent Victor Cachat's Evil Side isn't so much superpowered, as it just removes all stops in his already fanatical and determined character, turning him into a Death incarnate. Which tends to scare shitless those who know him only as a naive and timid Mister Nice Guy.
 * Multiple examples in the Skulduggery Pleasant books..
 * In The First Law trilogy, a perfect example of this trope is The Bloody Nine, Logen Ninefingers's powerful, chaotic and blood-thirsty alter-ego.
 * In Deltora Quest, when Steven is in danger, he.
 * In the Malus Darkblade series, the titular character can use T'zarkan, the daemon possessing him as this, but with a twist: each time it happens, T'zarkan gains a little more control over him.
 * In Hermetic Millenium, hero Menelaus also has houses the super-powered and amoral Iron Menelaus. Likewise with Del Azarchel/Iron Del Azarchel.
 * The Dresden Files have the Denarians, fallen angels sealed in silver coins. So much as touch the coin, and they get a free pass to the back of your mind, to convince you in any way they can to accept their power. Once you do, they go from backseat driver to Super-Powered Evil Side and grant you extreme power, at the low, low cost of your immortal soul. Over time, the human host starts to become as evil as the Denarian (if they weren't already).
 * In Wild Cards, The Radical has the combiend powers of all other alter-egos of Captain' Trips, thus making one of the most powerful aces. He's also, depending on where you stand, a Well Intention Extremist or a full-blown villain. Obviously he won't let Trips take back the control of his body.

Live Action TV

 * Niki in Heroes has her amoral alter ego Jessica ("ikiN"), who has sole control of her super strength
 * In the second season, it was explained that
 * A really beautiful Deconstruction is the British TV series Jekyll.
 * Lori developed one in the Big Wolf on Campus episode "Manchurian Werewolf" after being bit by a brainwashed Tommy. She became a member of the werewolf syndicate. Merton also got a dose of the evil life in "Everybody fang chung tonight" and "Boy who tried wolf" where he become a vampire and a werewolf.
 * Pretty much every Heroic Vampire protagonist or Supporting Character: see Forever Knight, Angel, and Moonlight.
 * Angel gets listed twice because he's from Trope Overdosed Buffy the Vampire Slayer.
 * Kamen Rider Kabuto's Tsurugi Kamishiro is actually, who actually manages to.
 * In Kamen Rider Kuuga, Kuga's Ultimate Form.
 * The Kamen Rider Decade version of Kuuga also possesses this form but . Taken further when he gains Rising Ultimate form which.
 * Decade gains an evil alternate form in his Violent Emotion form, which.
 * In the live-action Pretty Guardian Sailor Moon, . Pretty much the entire second half of the series is spent just trying to contain her, and upon the realization she can't be contained, at least minimize the damage she causes.
 * In the Farscape universe, starving Delvians start sprouting growths that paralyze any predators that touch them, turning would-be predators into prey. If that doesn't help, they'll start emitting spores, gradually paralyzing any and all lifeforms in the vicinity. In this state, higher cognitive functions are compromised, gradually turning them more and more feral. And if the said Delvian is Zhaan who was nice only due to her Heroic Willpower in the first place...
 * Buffy the Vampire Slayer has two of these:
 * If Angel loses his soul (due to the lingering effects of a Gypsy Curse), he becomes the brilliant and formidable Angelus, widely reputed to be the most vicious vampire in history. As Cordelia Chase once queried about Angelus's evident genius compared to his heroic alter ego's, "...what is it about evil that jacks up the I.Q. points?" More emphasis on the evil, though.
 * When Willow is pushed to the snapping point, she unleashes a Superpowered Evil Side in a bad way, replete with utterly delightful badass one-liners. I. OWE. YOU. PAIN.
 * The depth of this is such that Willow, the cutest, sweetest, and most innocent of the Scoobies at series start, becomes the only non-Giles member of the Scoobies to have directly murdered an innocent person. (Glory wasn't innocent, of course, but the human Ben was)
 * The emphasis here is on the superpowered - Dark Willow is arguably the most powerful known being in the Buffyverse.
 * Ah, but bear in mind Giles had the power of an entire coven of witches, and Dark Willow still smacked him down.
 * As time goes on, Willow seems to have her Super-Powered Evil Side under control. It's more that she turns evil when she uses powerful magic, but then she turns back good when she stops. A scene in Season Seven demonstrates this effectively: while using a powerful barrier spell to protect an innocent girl from a spider demon, Willow gets the black eyes and black hair, and also calls the girl a bitch. After the demon leaves, she goes back to normal, and apologizes to the girl.
 * Smallville:
 * Davis Bloome in Season 8 has perhaps the ulitmate Superpowered Evil Side in Doomsday, an alien Serial Killer and Person of Mass Destruction that is trapped inside of him. The good news: it's possible to repress Doomsday. The bad news: the only way to do it is for Davis to commit murders as himself, a fact that slowly drives him insane, even as it lets him access Doomsday's power while he's in his own body.
 * There's also Kal-El, Clark's Enemy Within who uses his powers a lot more efficiently and can even fly.
 * Sam Winchester, Supernatural. When he taps into the demonic "special child" aspect, he is extremely powerful (telekinesis, exorcism, torturing/killing of demons, immunity to attacks by demons) but loses all his humanity and morality and becomes arrogant, violent and cold. His eyes turn yellow or black on a couple of occasions.
 * Bo in Lost Girl has a major Superpowered dark side, draining a whole room of people of their life force when someone is about to kill her lover.

Mythology

 * Older Than Print: Cuchulainn in Irish mythology has a prime example of this kind of Unstoppable Rage. In the epic, Táin Bó Cúailnge, he enters a "Ríastrad" or "Warp Spasm." In this state he transforms into a horribly mutilated monster whose very appearance is enough to scare enemies away. The catch is that, while in this form, Cuchulainn may not know friend from foe. (See Slainé from Two Thousand AD to see just how mutilated he looks.)

Professional Wrestling

 * In 1996, Japanese wrestler Jushin Liger, who traditionally played the role of a face, unveiled his "Kishin Liger" heel persona, when he wrestled heel wrestler the Great Muta, who mid-match ripped Liger's mask off, revealing his "oni face". Liger's wrestling style would become notably more aggressive and heel-like in this persona.
 * This was also Mick Foley's schtick for a while in the WWE: when he needed a "boost" for a match, he'd come out as either his Mankind or Cactus Jack persona.

Tabletop Games

 * This crops up in the various Old World of Darkness Role Playing Games, especially those featuring Vampires and Werewolves.
 * One Tagline for the original Vampire: The Masquerade was "A Beast I Am, Lest A Beast I Become"—leeches had to allow themselves little atrocities like controlled blood-drinking to avoid being consumed entirely by the madness of their inner blood-hunger. However, while in the thrall of such a state, vampires can ignore wound penalties, which is a significant combat asset.
 * Werewolf: The Apocalypse: Werewolves, on the other hand, don't tend to view their own berserk frenzies as "evil" (after all, Rage is a gift from Luna... and they have plenty of reason to be really, really pissed off). However, if they give in to their Rage too fully, they can enter a state called "Thrall of the Wyrm," just like a normal frenzy, except that it's inescapable, and tends to provoke rather horrific behavior (typically either cannibalism, rabid dismemberment, or... erm... defilement).
 * Wraith: The Oblivion: Wraiths have got their Shadow, a second personality usually existing within the wraith trying to make them them give up their struggles and descend into nonexistence or permanently hand over control of their body. Depending on the Shadow, this might take many forms, some direct and some seemingly helping the wraith. The latter type often has ways to enhance the wraith's body when temporarily in control - better attributes, more magic powers or even items appearing only during the Shadow's catharsis. Such wraiths then always have the ability to let their Shadows handle combats too tough for them, but generally loathe to do so because there's no telling what else the shadow might do while in control.
 * The New World of Darkness keeps much of this:
 * In Vampire: The Requiem, vampires have the Beast within, which compels them to feed.
 * In Werewolf: The Forsaken, werewolves have two degrees of rage: one where they have to kill something, and another where they have to kill everything.
 * In Changeling: The Lost, changelings can get magic ("Glamour") from normal humans two ways—the first is by inspiring them to do something incredible. The second is to "ravish" them—make them feel despair. One example of this involved convincing a small child that the Fae in question had just murdered the Tooth Fairy.
 * Exalted has a couple instances where the characters go temporarily insane on some level:
 * The Solar Exalted might have this particular category nailed; one of their abilities—Ascendant Battle Visage—places them into a battle-trance that physically changes them to reflect their Battle Aura, and grants them intense and brutal combative skill. Remaining in this state too long, however, sends them into an Unstoppable Rage, at which point they become even deadlier, and fight until either they're dead or everything else that might be considered an enemy is dead.
 * The Ghost-Blooded (in the 1st edition at least) could learn a certain Arcanos called Lower Soul Ascendant, which fits this trope to a T -- increased physical power at the cost of embracing sociopathic behavior.
 * And to round out White Wolf's systems: In Scion, the Scion Companion supplement adds the Tuatha Dé Danann to the playable pantheons. One of their pantheon specific abilities? The "Rí­astrad" mentioned in the above mythology entry.
 * In Dungeons & Dragons 3.5, there is a prestige class called Frenzied Berserker. Once they've Frenzied, which is like a Barbarian's Rage but moreso, they attack until either the frenzy runs out, they are incapacitated/dead, they pass a will save, or there's nobody nearby.
 * Highly common in Warhammer 40,000, and one of the reasons Space Marines (Grey Knights in particular) are required to pass such rigorous and often deadly mental trials as a method of prevention. The most obvious are the Blood Angels Chapter and its successor chapters, whose members are known to succumb to a condition called the Black Rage which increases their already Super Soldier levels of strength and vitality and turns them into frothing berserkers who seek only death, often organised into aptly-named Death Companies led by skull-helmeted Badass Preachers. The Eldar however create one of these intentionally, inducing a form of split personality disorder so that in battle they can fight with unhindered skill and brutality while retaining absolute control over themselves the rest of the time. Then there's Chaos, which, being The Corruption and Exclusively Evil personified, fully embraces the added power this trope provides with no concern for the consequences, because "sanity is for the weak".
 * And then there's the Possessed Marines, who have a Superpowered Super Evil side.

Toys

 * Takanuva gets one of these in Bionicle, after having some of his Light drained by a Shadow Leech.

Video Games

 * For some reason, having an "evil/dark side" was a really popular game mechanic in the early 2000s.
 * Ryu, from the Street Fighter series of video games, has a power inside of him known as the "Satsui no Hadou", or Surge of Murderous Intention, which he works to suppress and was retconned as the reason that Sagat received the scar he bears on his chest. Akuma (Gouki in the original Japanese) represents someone who has fully given in to the Satsui no Hadou, and when he's not holding back, he is truly fearsome. In Street Fighter Alpha 3, 'Evil Ryu' is actually a secret, playable character - a dark-skinned, red-eyed version of Ryu with some additional attacks from Akuma's movepool.
 * Note that Akuma is an example of a character who has embraced the "Satsui no Hadou" but remains in control of his power at all times (he just holds back portions of it at various times). Ryu's Super-Powered Evil Side is a result of his being unable to control the power. However, since the power still involves a willingness to kill and a more brutal mindset even when in control, he makes no effort to even try to learn how.
 * In the third game in the recent Prince of Persia trilogy, the Prince occasionally transforms into an alter ego with a bladed chain-whip (and the skills to wield it gruesomely, out of nowhere) and who can completely regenerate whenever exposed to the Sands of Time, but at the expense of constantly deteriorating health otherwise. The Dark Prince is also a sociopath with a massive entitlement complex. Even when in the Dark Prince body, the Prince remains in control, but the Dark Prince hints that the health draining out of you is actually going into it, and that dying of this will give the Dark Prince control of the body (and, incidentally, Babylon).
 * Soma Cruz in some of the later Castlevania games inherited Dracula's soul, while Alucard is his son (sort of). The emergence of their Superpowered Evil Sides are Alucard's greatest fear and Soma's bad ending.
 * The Slayer from Baldur's Gate II, a ten-foot tall spiky mass of pure murder that the protagonist ends up gaining access to. Using it results in a reputation loss, except for scripted events that force you into it. Plus there's the whole thing about it killing you (and thus ending the game) if you stay in that form for too long.
 * And its Expy, the Ravenous Incarnation from Neverwinter Nights 2: Mask of the Betrayer.
 * Dizzy from Guilty Gear has a similar problem with one of her sentient wings. She's VERY powerful and unleashing her true powers causes her to lose control to her evil wing, Necro, who's motto is "Destroy everything!". With Dizzy being a Friend to All Living Things this really troubles her.
 * Not that the other wing, Undine, is much better. Unlike Necro, she won't attack anyone who comes within reach randomly, but she will annihilate anyone she perceives as even the slightest threat to Dizzy without even a second thought... and her definition of "threat" is just a little bit too broad for Dizzy's tastes. Do note that Undine is the wing that unleashes Dizzy's version of Gamma Ray... that says it all. Oh, and her tail has a will of its own too and often eats anything within biting reach.
 * Rozalin from Disgaea 2: Cursed Memories manifests a Superpowered Evil Side during the storyline when her seal is broken, which turns to be.
 * Mao from Disgaea 3: Absence of Justice has a similar Superpowered Evil Side that can.
 * From La Pucelle Tactics,
 * Iori Yagami in The King of Fighters is normally amoral, and (judging from his winposes) has quite a few screws loose. Riot of the Blood Iori, however, has absolutely no sense of self-restrain and will attack anything on sight.
 * Leona also fits this trope, sometimes even more perfectly than Iori, due to the fact that she is in the "good side", while Iori can't decide himself; with some Emotionless Girl spices added, though that said, she has smiled once.
 * Jaster Rogue in Rogue Galaxy does this, although his "evil" side isn't so much evil as so far above everyone else that he barely notices they exist. Hard to tell the difference from the "normals" point of view, though.
 * Johnny Garland gains this far into the third Shadow Hearts game.
 * In Xenogears, one of the primary villains for the first half of the game, Id,
 * This is subject to the variation mentioned at the top of the page. Even though Id doesn't get as much screen time as his alter-ego,
 * Grahf plays this role in two ways.
 * Zero of the Mega Man X series gains several powerful new abilities when he is exposed to large quantities of The Virus. When he is fully awakened by the Sigma or Zero Virus, he loses all of his emotions and his personality shifts to the one of an cold blooded killer.
 * In Mega Man Star Force Pat has a personality disorder. He'll randomly go into an evil state named "Rey" and punch someone. This foreshadows him fusing with Gemini and becoming Gemini Sparks W and B.
 * Elena's alternate personality Millenia from Grandia II.
 * Kingdom Hearts:
 * Anti-Sora from Kingdom Hearts II. Ironically, while Anti-Sora looks damn cool, he's not actually much more powerful than Sora in terms of offense, and can do nothing other than attack solo in a frenzy of clawing and kicking. The inability to heal, gain experience, or really do anything else makes this form a liability, and it can't be entered deliberately.
 * Riku, on the other hand, plays this trope straight in four of the games, but primarily in Kingdom Hearts Chain of Memories.
 * In Metroid Prime 3: Corruption, Samus gets the ability to enter Hypermode, fueled by the evil substance known as Phazon. Staying in this mode for too long corrupts her, leading to a Nonstandard Game Over, specifically turning into another Dark Samus.
 * Dark Jak from Jak and Daxter, after being exposed to Dark Eco.
 * And then they added a Super Powered Light Side along with Dark Jak in Jak 3. You use both to solve puzzles.
 * Sonic the Hedgehog has one in Sonic Unleashed. At night, he'll turn into Sonic the Werehog, a bulky werewolf-esque form of himself with super strength and stretchy arms. Though his personality remains more or less the same except for the obligatory howling.
 * This exception is Lampshaded after it is revealed that Sonic then asks, if it could be Chip who keeps him from succumbing to Dark Gaia and becoming evil when in Werehog form, to which Chip replies that he has nothing to do with him, it's Sonic's kind heart alone which lets him keep his sanity.
 * Sonic and the Secret Rings also introduced Darkspines Sonic, which was the result of sonic absorbing the secret rings of anger and sorrow. Notably, Darkspines doesn't just beat his enemy, he actually crosses the line Sonic usually doesn't and beats him to death.
 * In Super Smash Bros. Brawl, some of the Final Smashes have this effect.
 * Bowser's Final Smash transforms him into the even more monstrous Giga Bowser. Whether or not Bowser was evil to begin with depends on the game you reference...
 * Luigi's Final Smash, according to its trophies, is "a reflection of the Dark Side he embraced in his brother's shadow."
 * Almost every member of the Mishima Family in the Tekken series. Also Ogre/True Ogre.
 * Only Jin adheres to that fully with Devil Jin, however. Kazuya was evil all along; his Devil Form would be more like normal Super Powered self. And Heihachi is just that evil, he doesn't need an evil side to get more evil, super powered or kick ass.
 * Jinpachi could be said to be another example, as he holds the King of Iron Fist Tournament 5 to find somebody to stop him, as he could feel the Devil taking over. He also sends a letter to Wang, his old friend, to have a go as well.
 * In the early Soul Calibur games, Nightmare was supposedly a Demonic-Sword-induced version of this for Sigfried. The latter freed himself in SCIII, but his armour and residual evil power was too attached to Soul Edge to die.
 * Two far more definitive examples show up in SCIII as the boss Abyss (spawned from Zasalamel's quest for the power to die), and bonus boss Night Terror (Nightmare on serious 'roids).
 * Fighters Destiny has a clown character, and there's a cheat you can use which turns him into a werewolf.
 * Primal has its main character who personifies this when in any of her monster forms.
 * Subverted in Muppet Monster Adventure.
 * It is revealed in .hack//GU that Natsume has a split personality: Her normal self is her cheery, slightly ditzy self while her other self is crazed, rampaging Pker known as The Edgemaniac. This is played for laughs.
 * In the movie adaptation, Haseo's B-St Form is basically this trope incarnate. Even if all it did was make him look pathetic against the final boss...
 * Haseo's Avatar, Skeith, is also portrayed as this, although Haseo usually does a better job of controlling him than normal for the trope. Skeith is seriously scary when out of control, his actions being the only thing in the games that actually seem to frighten Haseo.
 * Vincent Valentine from Final Fantasy VII can transform into a variety of monstrous forms using his limit breaks. Possible forms include Frankenstein's Monster, Jason Voorhees and Chaos, the Big Bad of the first game in the series.
 * Does he really count? His transformations never seem to pose much of a threat to the party, so isn't it just a berserk Super Mode?
 * Terra's Esper form seems to be this in Final Fantasy Dissidia, as when she goes into it during the plot, she suddenly loses control and ends up fighting the other heros.
 * Django, the gun-slinging hero of Boktai. In the second game of the series Django is infected with vampirism and almost loses his soul before his half-brother Sabata purifies him with the Solar Pile. After this, Django eventually gains the ability to transform between human "Red Django" and vampire "Black Django." Though it might be argued that Black Django isn't that much more powerful as, despite his dark-based powers, he loses the ability to use all of Django's magic (gaining new spells only he can use) and is harmed by both rain and sunshine. In the third game, the transformation is changed to a "Trance" attack, where he becomes much more powerful, however the transformation only lasts a limited time, or until you leave the room.
 * The Terror Mask in the Splatterhouse series embodies this trope, especially in Splatterhouse 3 where its own personality, and its effect on Rick, become more apparent.
 * Queen Arshtat Falenas in Suikoden V took the Sun Rune into her to prevent it from falling into the "wrong hands." Ever since, she melodramatically rants and cackles authoritatively whenever her "divine rule" is threatened. Once, she even unleashed the Sun Rune, completely dessicating a lake and its nearby landscape and leaving her nearby subjects to die a wasting death. All in all, a Super-Powered Evil Side is a great way to balance The High Queen and her darker counterpart, leading to a natural aloof regality.
 * In The World Ends With You, the Bonus Boss is the Noise form of, and since he really kills you if you lose, it can be seen as this. The fact that, during the fight, he  could show that he's not quite in control.
 * Emil from Tales of Symphonia: Dawn of the New World has Ratatosk mode, where he morphs from a Woobie-ish Non-Action Guy into an ur-Badass Anti-Hero Blood Knight.
 * At one point in Wild ARMs 2, Ashley is transformed into some kind of zombie-like creature early on, but before he is taken completely, he makes it to the Argetlahm and pulls it out—this has the result of countering the demon within him with the good force of the sword, and the resulting combination is a badass black-armored-red-trimmed entity called Knight Blazer. He can't actually use it in battle until a few plot points later, but once he gains the ability, nearly every remaining boss fight in the game boils down to letting him transform in order to open up a can of whoop-ass.
 * In Mega Man Battle Network 4, if MegaMan turns dark enough from the use of dark chips, his dark side will appear after he is K.O.'d and start fighting. MegaMan gains control back after a while.
 * Chaos Shadow Soul in Battle Network 5 made MegaMan completely invincible and uncontrollable as the AI attempted to duplicate the player's fighting style. Speaking of which, the fight against Dark Rock in Battle Network 4 did the same, using every chip the player had ever used even the navi summon chips and giga chips and also can use all the program advances you done up to that point when you fight it and unlike the player version theres no warning when it uses them. it tends to favor using these.
 * The Suffering initially plays this straight with a "primal form" that shreds enemies but damages your Karma Meter. However, it's subverted twice over. First, you learn that . Then, the final boss proposes to "cure you"—and it sort of works. In the sequel, you can transform without harm, even if you're playing as a good guy.
 * The Fierce Deity Mask ("Oni Mask" in Japan) in The Legend of Zelda Majoras Mask turns Link into this. It helps that oni means "demon".
 * Legend of Mana has.
 * In Painkiller, when you collect 66 souls of enemies you killed, you transform into an unstoppable demonic killing machine. It only lasts for about 30 seconds but that's all the time you'll need to obliterate an area full of monsters just by looking at them.
 * It may not be on quite the same level, but in Pokémon Colosseum, there's a random chance that a Shadow Pokemon might go into 'Hyper Mode' during a battle. The Pokemon in question will be surronded by a black aura, and will do more damage - BUT. It won't be able to use any moves you've unlocked, it can't be healed, and it will also take recoil damage when it attacks. Thankfully, you can call out to it, which brings it back to it's senses.
 * Playable characters Dante, Lucia, Nero, Vergil from the Devil May Cry series all can transform into a demonic version of themselves with stronger attacks and health regeneration. In Devil May Cry 2 this becomes so easy it sucks, with the characters' demon forms not being thrown back, halted or even slowed by enemy attacks.
 * In Star Wars: The Force Unleashed Ultimate Sith Edition, you go into the ruins of the Jedi temple and eventually.
 * Dark Spyro in The Legend of Spyro series is Exactly What It Says on the Tin; Spyro's eyes turn white and his body gets covered in a flowing dark energy (that has a habit of clouding up the camera when gliding) and gives Spyro the fury element. It gets triggered when Spyro is overwhelmed in sadness, anger, or just a plain ol' BSOD. However, in The Eternal Night you can flicker it on and off at will in New Game+ (even in cutscenes!). He's shown to mostly have control over it though, as seen in Dawn of the Dragon.
 * Ryu from Breath of Fire 3 has the, which unleashes his ultimate dragon form Kaiser. When used by itself, the player has no control over Ryu, and he attacks at random (including allies!). Averted however, when . Using the flaw gene makes also the kaiser form controlable, but it is severely weakened.
 * In the same game you have also the Weretiger Form of Rei, which rises his attack power to high levels but he will also attack at random the party members. The problem with random attacking can be solved with the "Influence" skill. It can be learned from the Boss Goblin enemy.
 * In the same regard the "Berserk" Skill is identical to the Weretiger form, but it comes along with the downside that it kills you in three turns, it can be adverted with a Soul Gem or with the armor Manly Clothes though.
 * In The Warriors, every playable character has a "Rage" meter of varying length. When it fills up, the character can use a highly effective radial attack and their grapple specials become a great deal more violent, usually capable of outright killing an opponent regardless of health. Later on, you can even trigger it by using a healing item with full health. Subverted, though, considering that most playable characters are criminals of some sort.
 * Every single main character in Persona 4 must be recruited by defeating their Super-Powered Evil Side, or more accurately, their Shadow Archetype: the embodiment of all the things about themselves they can't stand to admit. The shadows have grown immensely powerful out of all proportion simply because being denied makes them stronger; once accepted, they become much weaker and "tame."
 * The series also gives us Black Frost-which is the horrific result of adorable Mascot Mook Jack Frost remembering he's supposed to be a demon after all. The process apparently renders him awesomely more powerful... and much more evil.
 * Unless you're playing Devil Survivor, in which case it turns him into a Pun-spewing Magical Girl-esque warrior of love and justice. ...And awesomely more powerful.
 * As Said in comics, Any Spider-Man game that has the option of the black suit has it as this. In Games such as Spider-Man 3 and Spider-Man: Web of Shadows his attacks become more violent and agressive, usually with Combat Tentacles and spike tendrils.
 * Subverted in Spider-Man: Shattered Dimensions, in which the Ultimate Universe Spidey (The one who actually has the Symbiote) is the kindest of the Spideys, he does have a Rage mode however (The only one with one) in which he becomes more scary looking and his attacks are more devastating, but his comments are actually the oposite. He'll say things like "Yeah, lets have some good old fashioned RAGE!" and "Raaage! I'm not actually angry, I just like saying it."
 * But it's justified, since Madame Web is using her powers to keep the suit from taking over.
 * This is the reason the quaggan have survived in the Post Apocalyptic world of Guild Wars 2 despite being Actual Pacifists; actually manage to piss them off, and they turn into what is best described as a cross between an orca and a bulette, with absolutely no regard for their safety or collateral damage. And when they calm down, they'll apologize for it.
 * Mu-12 is this for Noel Vermillion. It should also be noted that Mu is her original form, similar to the Elfen Lied example above.
 * Hawke from the Dragon Age II "Destiny" trailer exhibits this, gaining Red Eyes, Take Warning when he resorts to Blood Magic to Curb Stomp Battle the Arishok.
 * Similarly, any time a Mage Hawke uses Blood Magic in-game, it could be seen as tapping into this.
 * Anders literally has one in the Spirit of Justice, constantly having to fight to maintain control after his own anger corrupted it into a Demon of Vengeance. When he loses control, he gains Glowing Eyes of Doom, a Booming voice, Volcanic Veins and a Battle Aura.
 * To an extent  in Asura's Wrath is this, and is also a One-Winged Angel transformation: It's something of a Shout-Out to the Naruto Example above, as well as the .hack GU movie's B-ST form. It helps that the guys that made Asura's Wrath make .hack and the Naruto Ultimate Ninja games.

Visual Novels

 * The "Shiki Nanaya" within Shiki Tohno in Tsukihime. Crucial in the manga/game but only used once (and not explained) in the anime. Interestingly enough, Nanaya isn't really superpowered, evil, or even a personality. It's really more of a mode that activates in times of extreme stress or due to close proximity to non-humans. In other words, Shiki is still in full control, and he's still consciously guiding his actions, just with about two tons of bloodlust propelling him. Also, all it really does is boost Shiki's speed and dexterity (his ability negates the need for strength), and even that came from the training he had in his youth.
 * In Kagetsu Tohya it's revealed that his super powered demon killing side terrifies him. As such, he actually appears to have stopped using it.
 * Many other characters in the Nasuverse have an 'inversion impulse,' the desire to go psycho and unleash their bitchin' superpowers on the world in an orgy of murder. Being a true ancestor or successor to a demonic or psychic bloodline helps. Sometimes, such as in Shiki Ryougi's case, this a true split personality, in others it's just buried bloodlust or some less conventional psychological artifact. In Arcueid's case, being a True Ancestor means using most of her insane amount of power simply repressing this impulse; letting loose would increase her power orders of magnitude.
 * Melty Blood, the fighting game based on Tsukihime and Kagetsu Tohya, uses the Big Bad's plot-device-like powers to summon the Super-Powered Evil Side of several characters, which leads to interesting pre-fight exchanges in "Doppelganger" fights.
 * In the Heaven's Feel route of Fate Stay Night, 's Super-Powered Evil Side is powerful enough to defeat . She also turns, herself a Super-Powered Evil Side version.
 * Both also play with this trope quite a bit. In 's case, this trope is subverted when it's revealed that her Super-Powered Evil Side is not in fact another personality nor really evil (though still superpowered) and that she's still the same person as who she used to be, and that she actively and consciously invoked this trope to push away the responsibility for her actions. And while it's not explicitly stated in 's case, it's implied heavily that she's still the same person as who she used to be as well.
 * Akai Ito: Tsuzura's fox-mage mode. It's even played as what-do-you-mean-it's-not-rape the first time she taps into it and can't control it.
 * Aoi Shiro: All who wield the <> are prone to this, but Sword-Demon Kaya (your Back from the Dead Rather Wrongly big-sister-figure) especially... leading to a lot of Nightmare Fuel Bad Ending.

Web Comics
": Who knows what kind of sadistic and impossible stuff I'll do now."
 * Roger in CRFH. Unleashing his werecoyote side is often the Roomies' only way out of a tight spot, but he has trouble controlling it, and he's been warned by another werecoyote that sooner or later he'll be unable to change back.
 * He actually has a second werecoyote form that is a stronger embodiment of this trope.
 * Graveyard Greg of the Gaming Guardians has two separate and unrelated evil sides. Not only is he a werewolf, with an animalistic but self-aware wolf personality, but he's also possessed by a voodoo spirit which can take control of him at times. Greg has retained control by pitting them against each other, until they decided to team up to suppress him, becoming a zombie wolfman which calls itself "Mange".
 * Last Res0rt has Jigsaw, since apparently all vampires in her galaxy can transform during their Unstoppable Rage.
 * In Jack, the eponymous character, a personification of the sin of Wrath and the Grim Reaper, will occasionally enter a kind of "Wrath Mode". In this state, he will be overcome by his sin and gain a boost of power. He later
 * While 'Fallen Grace' (AKA 'Dark Omega Grace') from El Goonish Shive falls much closer to the Crouching Moron, Hidden Badass type, she still deserves mention here. Not only is Fallen Grace actually willing to use her shape-shifting powers as a weapon - unlike the pacifistic (NOT Technical Pacifist) Grace - she's also got access to the Lespuko Spurs; special claws that retard healing, thus neutralizing the advantage of the Healing Factor. She's also got horns, Hellish Pupils, and a whole lotta spikes.
 * In Gnoph, Will's symbiotic partner Lyss usually acts as a Bond Creature; but when he passes out and she takes full control of his body, she acts like an example of this trope, due to being Ax Crazy and having no compunction against killing (or eating) humans.
 * Subverted in The Order of the Stick: It initially looked like the comic was going down this path when Vaarsuvius made a deal with three fiends in order to save the lives and souls of his/her family. Having successfully rescued them from a dragon, (s)he then proceeded to The next strip reveals that, contrary to what the devils said earlier, the power-up had no effect on Vaarsuvius' ethics and that whatever atrocities (s)he just committed were all of his or her own doing.
 * 8-bit Theater:
 * Black Mage encounters himself in the Castle of Ordeals, where the Light Warriors have to face symbolic representations of their own flaws. However, the only thing that could represent Black Mage's flaw (Pure Evil) was himself, as nothing else was evil enough. Then it turned out that the even his own duplicate didn't quite represent some of the more evil things he'd done, which corrected itself as the real Black Mage ran through them by becoming even more evil (as well as powerful). He then absorbed his own evil and power back into himself, eventually unleashing it to destroy four other incredibly evil beings, whose own evil and power he then absorbed, giving him an evil aura as well as incredible magical power.
 * Later . Lampshaded thus:


 * Trace Legacy has one of these. Whenever he gets extraordinarily pissed off, his memories of his old life cause a person shift. However recent comics have seemed to show this side is merging with is current persona. (As the racist evil side is shown defending Keidran, which is something only his normal persona would do.)
 * Subverted in Homestuck:
 * from Noblesse slips back to his Mad Scientist persona when he unlocks his power, which allows him to curb stomp ABSOLUTELY EVERYONE. His Slasher Smile has to be seen to believe it.
 * In some of Zeurel's Original Character Tournament entries such as Law of Talos and Escape From Nevara, Black Ace is this to Spoiler.

Web Original
"Caboose: Now I'm thinking of a kitten... covered in spikes... that makes... me... angry... YYAAARRRRGGHHH! Caboose jumps off the roof he was hiding on, shaking the ground when he lands Caboose: My name is Micheal J Caboose, and I. Hate. Babies! Red Zealot: It's the beast! The Anti-Flag! Come to live among us and rule for seven years! The end is nigh- blleergh!"
 * A fairly goofy example occurs in episode 40 of Red vs. Blue: in order to fight off a horde of "noobs" in Battle Creek, Caboose gets in touch with his "angry side", which results in him gunning down the noobs while shouting bizarre threats like "I will eat your unhappiness!" and "Your toast has been burned, and no amount of scraping will remove the black parts!"


 * He did this by replicating the effects of being possessed by the AI O'Malley, who gives whoever he inhabits a Super-Flanderized evil side, which in Tex's case makes her super aggressive. When he inhabited Grif he wanted to Take Over The World, but was too lazy to do anything. Only Church is immune to this effect, being as cynical as it is possible to be already. Among other reasons...
 * In Tales of MU, the side of Mackenzie that some fans have taken to calling Kenzie is two details off from being a textbook example of a Superpowered Evil Side: First, Kenzie is triggered by hunger instead of desperation in battle. Second and more distancing, the closest thing to a superpower Kenzie has over normal Mack is being willing to hurt people that are trying to kill her.
 * Shandala in Broken Saints has some serious issues.
 * In the DCU role playing universe of JLA Watchtower/DC Nation, Fauna, a sweet, quiet Granola Girl shapeshifter has this problem if you push her too far. Also, the more complicated her shapeshifting or extensive the use of her other abilities, the more feral she becomes.
 * In the "Angry Video Game Fag" by Ebeeto, Ebeeto "transforms" into The Angry Video Game Fag whenever he is angered enough. The transformation comes complete with a video game inspired cutscene.
 * Flippy of Happy Tree Friends, whenever he's reminded of the Vietnam war.
 * Spoony treats Dr. Insano as this in Kickassia.
 * In the Global Guardians PBEM Universe, Josiah Brimstone is a skilled and powerful sorcerer, but when his spells are not enough, he can unleash his inner demon on the bad guys. The inner demon doesn't always stop at beating down the bad guys, though, so Brimstone is really reluctant to do this. Viviane von Klause, the "Witch of San Francisco" tries to avoid overusing her magical abilities because if she goes too far and pushes her magic too far, the ghost of her Satanist grandmother takes over for a little while.

Western Animation

 * My Little Pony Friendship Is Magic gives us Princess Luna, whose own jealousy and bitterness (and according to Word of God, an inkling of dark magic) transformed her into the evil goddess Nightmare Moon.
 * Dragons are prone to greed, and the greedier they get, the bigger and stronger they get, which makes them even greedier. In "Secret of my Excess", a few extra gifts on his birthday awaken Spike's dragon greed, and he becomes a huge rampaging full-grown dragon taking everything he wants from Ponyville.
 * In the Teen Titans cartoon, a splashing of chemicals prompts good-natured vegetarian Beast Boy to turn into a surly, meat-chomping bad boy who later turns into an anthropomorphic wolfman that was capable of taking on the entire team (as well as another wolfman). Later it's explained that, instead of turning Beast Boy into an actual lycanthrope, the chemicals only unleashed what was already there (which makes no sense considering that ), and he's given an antidote so that he won't transform against his will. He once again manifests this hidden wild side in a battle against Slade, slicing through a number of his goons before Slade puts a stop to it with his own supercharged powers.
 * Possible subversion: It's made quite clear that "Man-Beast" isn't evil, just a really powerful, rather intelligent animal. Like any animal, it becomes hostile when scared, but generally it keeps to its human form's wishes. Beast Boy still expresses concern that it's still inside him at the end of the episode.
 * He does seem to have acquired a degree of control over it later on, though he rarely uses it. In its first appearance, though, the Beast is more like the Hulk—not evil, but uncontrollable, volatile, and dangerous.
 * And of course, there's Raven's "Daddy Issues". Dr. Light should really have backed off like she told him.
 * Kim Possible: Ron Stoppable is ordinarily a likable goof, but he's been zapped a couple of times with Applied Phlebotinum with superpowered evil results. The first time, the device was malfunctioning and gave him a transfusion of Dr. Drakken's evil, turning him into the insane, fiendish, blue-skinned, cleverer-than-Drakken-by-a-long-shot "Zorpox the Conqueror." The second time, the device was a properly-working instant Mirror Morality Machine. One might simply chalk it up to a removal of inhibition, of course, as Ron has some serious mystical mojo that backs him up at critical instances. The point is, Ron's evil side is inexplicably hyper-competent to the point of being slightly unnerving (enough to cow Shego into obedience) -- he mastered the art of having multiple plots within what may well have been hours of his conversion, and showed himself to be a serious, focused martial artist, at least the equal of Kim. Granted, he HAS had secret ninja training...
 * Ron loses focus easily, his evil side doesn't. When Ron gets focused, he becomes competent. But where the heck did his evil side get the skills to invent that plasma catapult thingy?
 * That time he had Drakken's evil, which probably included his Evil Genius (Hey, it makes as much sense as having it include his blue skin).
 * He may be Book Dumb or Brilliant but Lazy—for example, the doom machine that Drakken forced him to build actually worked and was made in a CAVE!! WITH A BOX OF from scrap. And in a cutscene from the game A Stitch in Time, kindergarten-age Ron is capable of giving a complex speech. Word of God actually suggests that he may have repressed his genius to fit in better.
 * He channels negative emotion into action a lot better than positive happpy emotion. Taking over the world is a negative emotion. He also channels his powers when someone hurts Kim. He just does a lot better when in angry mindframe.
 * Transformers:
 * An Applied Phlebotinum instance is Rhinox being turned into a Predacon in the Transformers: Beast Wars episode "Dark Designs". He's an ideal minion on the surface, but beneath it, he's cunning, capable, and extremely aggressive, quickly taking it upon himself to create chaos in a takeover bid, which almost works until Megatron applies Reverse Polarity to the Applied Phlebotinum just in time to keep Rhinox from finishing him off. Good thing for Megs that Evil Rhinox just had to gloat like any other bad guy would have, huh?
 * Megatron clearly learned his lesson from his ill-fated attempt at turning Rhinox evil in Beast Wars.
 * Another example involving Rhinox shows up in Beast Machines when it was revealed that
 * Some poor, misguided fools seem to have heard that G1 Grimlock is capable of combining with the Dinobots to create "the Beast," a terrifying titan of destruction and primal rage. These people are damned liars. Or at least, weren't aware that the sheer suckitude of that Story Arc was so much that Unicron and the Autobots teamed up to wipe it from space and time.
 * A literal form of this is The Batman version of Clayface. Just using his powers turns him insane and monstrous.
 * In Earthworm Jim, whenever Jim's puppy sidekick Peter is injured, he turns into a hulking, ravenous mutant whose sole goal in life seems to be beating Jim to a pulp. In a joke inversion, Peter's Evil Twin is evil when "normal", but his psycho mutant form turns out to be good.
 * The 2006 revival of Biker Mice From Mars has Stoker turn into an insane rat-like beast called Stoker rat.
 * An episode of Mr. Meaty had Parker (who is normallly calm under pressure due to the fact he just blissfully takes all those insults people kept throwing at him in) turn into a Hulk-like monster due to being unable to hold all those insults in any longer.
 * In an episode of The New Adventures of Batman (the one after Batman the Animated Series), Batman inhales an anti-fear toxin made by the Scarecrow. As a result, Batman has no fear. NONE. At one point, Bruce Wayne (that's right, no disguise) infiltrates some facility and has to deal with a moat with an alligator or crocodile. He walks through the moat, becoming completely submerged. While still under water, sends the animal flying from the moat and continues on his merry way.
 * Distinctly more of an Superpowered Id than Evil Side, but Freakazoid! is like this to mild-mannered nerd Dexter Douglas.
 * Coop on Yin Yang Yo. In his regular form, he's weak and nerdy. However, when he's infused with The Night Master's power, he becomes a match for Yin and Yang.
 * When audiences found Invader Zim's GIR cute, the writers created an episode where Zim actually fixes him - and he becomes suddenly destructive and hyper competent, determining the only way to conquer Earth is with Zim out of the picture...
 * A flashback in episode 19 of Generator Rex reveals that Rex can turn into a savage biomechanical Giant Robot Evo. One of the reasons White Knight is so hard on Rex is because he is afraid of Rex becoming that monster again. Rex himself has no clue he can do this thanks to his amnesia.
 * Avatar: The Last Airbender: The Avatar. When the vessel for the Avatar is threatened it locks into a superpowered mode that controls all the elements; it cares only for the protection of the current Avatar and to uphold the balance of the world. In a proper one-on-one battle, it is nearly impossible to deafeat.
 * The story is able to avoid the question 'of why doesn't he always go into this mode' in two ways. 1) While the Avatar isn't evil, it is highly destructive. Aang in particular, a vegetarian Technical Pacifist is terrified of the Avatar State, and how it doesn't uphold any of his personal morals. 2) The Avatar State is also the only time that the Avatar can be truly 'killed', as death in that form will stop reincarnation for occuring.
 * This was actually the whole focus of two separate episodes. One General outright claims that they can win the entire war by turning Aang into a living WMD by dropping him in the Fire Nation while in the Avatar state. While he was aware that Aang was unable to consciously trigger it, he also didn't think far enough ahead, namely that Aang didn't have an off button either. The second episode specifically focused on Aang being able to control and command the Avatar State.
 * From Iron Man: Armored Adventures: Gene Khan, though already the villain, has the ability to transform into the far more menacing Mandarin.
 * In Winx Club, Lord Darkar uses his dark magic to turn Bloom into her Super-Powered Evil Side in the form of Dark Bloom, who is basically Bloom with a black version of her fairy outfit and demonic yellow eyes. And he does it twice with her in the second season. Once to have her ship off Alfea's Codex piece to him through his Team Pet Kerbog, and again to have her help him open the portal to Realix with the four Codex pieces where he can acquire the Ultimate Power. Both times had her turned back to normal in the end - for the first time, the impostor Professor Avalon used his wand to lift the spell, and for the second time, it was Prince Sky who changed her back through his words of kindness, especially his "I love you" line, after which she returns the Ultimate Power to its rightful place to Darkar's shock and dismay.
 * One episode of Xiaolin Showdown was about Dojo transforming into an evil monster and destroying everything in his path after Omi accidentally frees him from his cage.

Real Life

 * The nigh-mythical Norse berserker rages, an adrenal and psychosomatic overclocking which gave one the ability to ignore mortal injuries but removed one's ability to distinguish friend from foe. The less brave soldiers simply drank a lot of alcohol.
 * However there is little consensus as to how effective the rages were, or if they even existed, some historians attributing these accounts to overwhelming fear of the Norseman, a likely scenario considering the Norse's tendency to attack and loot monastaries (being non-Christian and thus seeing no importance in them other than being very wealthy), which was the feudal equivalent of crossing the Moral Event Horizon.