One-Winged Angel/Web Comics

"Sorcerer: "Enough games! With all the powers of HELL at my command, I now take the form of the Ultimate Destroyer, a [...] fiend so diabolical, so terrible, that all who lay eyes upon his visage fall into..." (his bad guy monologue drones on the background) "...yeah, he's going to turn into a dragon, isn't he?" "Seems rather clichÃ©. Perhaps a giant octopus with multifarious appendages?" "No. Giant snake for sure.""
 * El Goonish Shive has a handful of them:
 * Hedge plays it normal, able to turn from a normal guy into a beastly hedgehog-man form, though he prefers to stay a hedgehog being most of the time and it counts as a Reveal when his human form turns out to be handsome.
 * Due to the incident that produced Ellen (long story), Elliot wound up permanently able to change into the cat-man form he'd asked Tedd to zap him into afterwards in order to chase her down. Unlike most examples, though, he didn't know he could do it until he involuntarily did it again to fight Hedge. Which knocked him out.
 * Grace has a metric buttload of One-Winged Angel forms, most also of the Cute Monster Girl variety. Except for her Omega form, which turns her into a feral squirrel with horns and razor claws. And she's ferocious, as opposed to her normal bubbly self.
 * Vlad does this in reverse. Ellen zaps him with a Gender Bender ray, turning Vlad the part bat, part bird, part Nightmare Fuel monster-man into Vladia, the relatively normal girl, the only change Vlad's likely to undergo due to a Painful Transformation problem that nearly killed him the last time he tried to be human: she's not sure she'll survive a gender shift, and doesn't want to risk it now that she's finally human.
 * It wouldn't be a proper RPG-spoofing webcomic if Adventurers! didn't have an instance of this. (Also pictured in title)
 * Parodied much earlier in same with "Wing-B-Gone!" Which brings up a good point: wouldn't this be really inconvenient?
 * Lampshaded in Golden, when the villain sorcerer decides it is times to turn into his combat form to end the protagonists, and promptly turns into... a binturong with white spots. (And not a badger at all, whatever anyone is saying, no Sir.). The protagonists even comment on this:


 * Wyler, a rich, weak mastermind from Art of Fighting 3, became one after drinking an elixir that more or less turned him into The Incredible Hulk.
 * One of Prof. Broadshoulders' (from Zebra Girl) defining characteristics is a "Mr. Yuk" face branded onto his forehead. Turns out
 * Inverted in archcriminal Fructose Riboflavin's first appearnce in The Inexplicable Adventures of Bob. He first appears disguised as a handsome, muscular human, and does all his ranty monologuing in that form. It's only after his scheme has failed that he drops the disguise as pointless, revealing his mildly creepy but not very frightening wizened old alien form.
 * Parodied in this Sunday At Ten strip.
 * In Acorn Grove you only get a hint of the devil's true form in silhouette. Can't really make out anything other than lots of tentacles.
 * In The Non-Adventures of Wonderella, Nixon supposedly does this.
 * 8-bit Theater has
 * In Problem Sleuth, Mobster Kingpin's imaginary self becomes Demonhead Mobster Kingpin for the final battle, which takes up nearly half the story.
 * Sluggy Freelance features a random Mook getting infected with a "Cheesy Bossmonster Virus", which is this trope in a tube.
 * In the "Holidays Wars" story, there's one on both sides: Bun-bun becoming  and fighting Santa Claus who had   (It doesn't really make sense in context, it's just Crazy Awesome.)
 * Homestuck has this sequence, in which The Starscream uses a Game Breaker weapon to and then kill, then proceeds to take the Ring of Power. Which turns him into an evil, two-winged two-tentacled one-armed cat-faced sword-impaled harlequin-garbed Eldritch Abomination. Nightmare Fuel indeed.
 * It gets worse, though his appearance gets less ridiculous as the last prototyping's power overrides some of the previous elements. He has been shown to be able to return/retract them (at least the tentacles).
 * Lord English is essentially this to, although it's not so much transforming as it is
 * Oosterhuis/ from Panthera plays this transformation near perfectly. He even seems to win the first encounter, too.
 * Referenced by name in this VG Cats.
 * The end boss of Adventure Dennis.