[[quoteright:350:[[TabletopGame/MagicTheGathering http://static.tvtropes.org/pmwiki/pub/images/Transmutation2_3337.jpg]]]]
[[caption-width-right:350:[[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=2819 This]] [[HurricaneOfPuns fairy's tale just got very point-nant.]]]]

->''You saw the beauty side of me before! Now, with great pleasure, I introduce you to the BEAST!''
--> -- '''Zarbon''', ''Manga/DragonBall''

A Power Upgrading Deformation will make a character or creature much stronger but also make them look at the [[UncannyValley least]] [[WhatMeasureIsANonHuman inhuman]] and at the [[BodyHorror worst]] [[EldritchAbomination horrendous]]. Unlike the PsychoSerum where an ugly appearance can be a side effect, for the Power Upgrading Deformation the newly ugly appearance is the ''source'' of the enhancement: like sprouting CombatTentacles, pincers, [[GrowingMusclesSequence supermassive muscles]], MyBrainIsBig, [[TheGrotesque grotesque]] {{Cyb|org}}ernetics, etc. Because of this it would technically still be considered a MagicEnhancement or SuperSerum and not PsychoSerum.

If the setting has a BishonenLine, this drug, technology or spell will take the character to ''just'' before the return to prettiness (or if already there, start the cycle over). It's also worth noting that protagonists and main villains may get off easy with [[ButYourWingsAreBeautiful cool looking alterations]] that are [[OneWingedAngel way more]] [[SuperMode powerful]] while {{Mooks}} and secondary characters aren't so lucky.

The deformation may be a mix of: permanent (requiring a cure to remove) or temporary (granting a SuperMode), and perfectly stable (no more {{muta|nt}}tions) or continuously changing (risking falling to TheCorruption or PowerDegeneration). Because its effects are so nasty taking it tends to be treated as a GodzillaThreshold, with [[EmergencyTransformation only the direst of situations meriting it]]. Villains like the MadScientist and EvilutionaryBiologist will delight in kidnapping victims to use this on... usually paired with a MindControlDevice of course! [[note]](Can't have a PhlebotinumRebel, now can we?)[[/note]] On the other hand, some villains may [[ProfessorGuineaPig take it themselves]], become a OneWingedAngel and proclaim AGodAmI! Truly, EvilMakesYouMonstrous. Mind the ClippedWingAngel from overdosing.

Compare DangerousForbiddenTechnique, EvolutionPowerup, OneWingedAngel, and TransformationOfThePossessed. See also BeautyToBeast and DeadlyUpgrade. Pretty much all {{Lovecraftian Superpower}}s result in this.

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!!Examples:

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[[folder: Anime and Manga ]]

* ''Manga/{{Berserk}}'': When [[EliteMook Zondark]] [[CurbStompBattle is unable to defeat]] [[AntiHero Guts]], [[AristocratsAreEvil the Count]] makes him [[OrificeInvasion swallow a part of him]]. This not only makes Zondark physically more powerful, but gives him the ability to grow CombatTentacles to replace lost limbs. The Count himself is one of the many [[OurDemonsAreDifferent Apostles]], [[DealWithTheDevil who have all been]] [[WasOnceAMan originally human]]. The Apostles can assume a human form but when they go OneWingedAngel [[BodyHorror "deformed"]] [[EldritchAbomination is an understatement]].
* In ''Manga/{{Claymore}},'' this is how the titular SuperSoldiers are made, grafting in a piece of demon flesh to give them some of it's powers, but they eventually succumb to TheCorruption, if they don't give in to their SuperpoweredEvilSide.
* The Tavoo/Taboo race in ''Manga/{{Psyren}}'' all have a core known as an Illuminus, which heightens their psionic abilities, but often disfigures them to the point of not even looking human anymore, usually taking on an [[EverythingsWorseWithBees insectoid]] appearance instead. The few exceptions are the high-ranking W.I.S.E. members, [[DoubleStandard and several others such as Tatsuo and Alfred.]]
* Similar to ''Claymore'' example, if the [[spoiler:Magical Girls]] of ''Anime/PuellaMagiMadokaMagica'' falls into DespairEventHorizon, they will turn into [[spoiler: [[EldritchAbomination Witches]]]]. This is actually a [[SubvertedTrope subversion]], since [[spoiler:Witches]] lose their sanity and acts purely on instinct, making them less effective in actual combat.
* The Zoanoids in ''{{Guyver}}'' are basically mutated humans whose new (revolting) forms are always tailored to give them a specific strength or super attack. [[MonsterLord Zoalords]] are however higher on the BishonenLine and look far less ugly than their underlings.
* Zarbon in ''Manga/DragonBall Z'' has a powerful second form, but it makes him look fat and ugly (whereas his normal form is a GorgeousGeorge type), so as a matter of vanity he avoids using it.
* ''Manga/{{Bleach}}'' gives us Ichigo's Hollowfication, as well as the Vizoreds who have similar powers. By tapping into their inner Hollow, they gain immense strength and speed, but have a bone-like demonic looking mask grafted onto their faces in the process. It is only temporary though. The mask can be broken off in battle, and it'll eventually crumble away in time. The mask's appearance varies from person to person, but all of them stop looking human.

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[[folder: Comic Books ]]

* In TheNewUniverse in general and ''Comicbook/{{DP7}}'' in particular, [[MassEmpoweringEvent the White Event]] makes people suddenly have power-related mutations, many of which are like this. Moreso minor characters than the main ones, which [[CursedWithAwesome for all their complaints are really not that bad]].
* Creator/{{Marvel|Comics}}'s ''Comicbook/TheIncredibleHulk'', Dr Banner transforms into a giant green rage monster and has mega strength.
* In the {{New 52}} reboot of ''ComicBook/AnimalMan'', Buddy Baker now actually physically changes shape when he uses animal powers. The transformations are NOT pretty.
* The ''ComicBook/FantasticFour'''s The Thing is perhaps one of Creator/MarvelComics most iconic examples. After passing through a cloud of cosmic radiation he grew a [[SuperToughness super tough rock-like hide]] and SuperStrength to match. The downside is that unlike Reed, Sue and Johnny he ''can't'' turn his powers on and off, and is always the same huge frightening rock monster; an issue which has caused him no end of grief and in some continuities even suicide attempts.

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[[folder: Film ]]

* In ''Franchise/PiratesOfTheCaribbean'', Davy Jones and his crew are immortal, but have spent so long neglecting their job of {{Psychopomp}} for the dead at sea that they've become [[HalfHumanHybrid half-morphed into sea creatures.]]
* In the live action ''Film/StreetFighter'' movie, the project behind creating Blanca is basically an attempt at creating mutant {{Super Soldier}}s and brainwashing them.

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[[folder: Tabletop RPG ]]

* Just about every Chaos mutation in ''[[TabletopGame/{{Warhammer}} Warhammer Fantasy]]'' and ''TabletopGame/Warhammer40K'', since these mutations include things like CombatTentacles, pincers, extra mouths, cancerous growths...
** In 40K, most augmetics (metal replacement parts, ranging from bionic eyes to replacement arms to [[{{Spider-Man}} Doctor Octopus]]-[[SpiderLimbs style dendrites]]) are rather crude and ugly (ork versions are even worse). The Adeptus Mechanicus see the replacement of flesh with metal as the ultimate way to better themselves, so naturally they get [[UncannyValley the worst reactions]] from normal humans.
** Even becoming a Space Marine, the de facto "heroes" of the 40K universe, involves some pretty gruesome procedures, like the addition of extra organs, genetic modifications that lead to superhuman size and musculature, metallic/ceramic replacements for your skeleton, and an implanted "second skin" that interfaces with your PoweredArmor. Worse still, many of these upgrades are based on non-renewable implants that have to be harvested from dead Space Marines so they can be passed on to new recruits!

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[[folder: Toys ]]

* In the fifth story line of ''Franchise/{{Bionicle}}'', the Toa Metru are captured and injected with [[TheCorruption Hordika venom]], which turns them into [[BeastMan half-animals]]. [[DownplayedTrope Downplayed]] in that while greatly increasing their physical strength, it also degrades their elemental abilities to some extent.

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[[folder: Video Games ]]

* The basis for Splicers in the first two ''Franchise/BioShock'' games. Specifically, they were users of a gene-modifying substance called ADAM- and along with the many cosmetic uses that it can be applied to, specially-prepared batches can give the user superpowers in the form of plasmids; unfortunately, abuse of the substance has resulted in addiction, disfiguration, and insanity. The main characters can also suffer a few of the tamer side-effects when they have plasmids equipped: [[PlayingWithFire Incinerate!]] clearly burns the wielder's hand; [[AnIcePerson Winter Blast]] causes icicles to grow through the user's flesh (complete with blood); finally, [[BeeBeeGun Insect Swarm]] results in a mixture of nasty-looking stings across the hand (in Jack's case) or a honeycomb forming out of the palm (in Delta's case).
* This comes up in ''VideoGame/DeusEx''; some cyborgs dislike the protagonist because they had to sacrifice their ability to look normal (thanks to the fairly obvious nature of their implants) while the protagonist's nanomachine based augments have barely any cosmetic effects (not to mention rendered them obsolete).
* [[EldritchAbomination Bydo]]-derived OrganicTechnology from ''VideoGame/{{R-Type}}'', under certain circumstances. For example, if the Claw Force is detached from the fighter too long, it temporarily mutates and goes on a rampage.
* In ''VideoGame/DigitalDevilSaga'', everyone infected by the demon virus has access to demon form, which is stronger than human form. Said demon form ranges from looking vaguely humanoid (most of the main characters) to slimes to the [[EldritchAbomination worst looking of]] Franchise/ShinMegamiTensei [[EldritchAbomination demons]].
* Dr. N. Brio's appearances in the ''Franchise/CrashBandicoot'' series usually involve him drinking [[PsychoSerum mutagen]] and turning into a [[ComicBook/IncredibleHulk hulking green monster]] (though by the time of ''Crash: Mind Over Mutant'', it seems like he needs the mutagen to ''keep'' from transforming). [[spoiler:At the end of Mind Over Mutant, Dr. Cortex samples the mutagen himself, with similar results.]]

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[[folder: Western Animation ]]

* ''WesternAnimation/{{Kaijudo}}'' has the Choten's evolution drug, which transofrms the series' normally one-form {{Mons}} into a new, stronger form.
* ''WesternAnimation/StreetSharks'' has the gene splicing treatment that turns humans into sharks (and sea animals into monsters).
* Every ''Franchise/TeenageMutantNinjaTurtles'' cartoon had the mutagenic ooze which made them more human-like, while also mutating humans into uglier mutants.
* The splicers in ''WesternAnimation/BatmanBeyond'' used genetic engineering to become {{Half Human Hybrid}}s, which generally while animalistic weren't ugly. When their boss fights Terry, he takes a boat load of them and goes OneWingedAngel... until Terry gives him a ''second'' round of drugs which pushes him into ClippedWingAngel.

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