In the MSF High Forum, The Manager Has made the mistake of checking to see if the snake he just nearly fed two PCs to is okay. Good news! The snake is okay. Bad news! It's in a bad mood.
Also occurs in MSF High proper, for the first female-to-male TG in the comic.
In general, any Web Original story in which a character maliciously causes sexualized transformations has at least a 20% chance of applying this trope. See also: countless stories on Fur Affinity.
While Let's PlayingNew Super Mario Bros Wii, The Runaway Guys frequently abuse the bubble mechanic. This can backfire when the sole player who's not bubbled winds up dying. In particular, Episode 14 illustrates this well — in part by being the first episode of that Let's Play that had to be broken up into two videos due to its length...
Sociopathic Hero Jobe of the Whateley Universe created a serum that would let him turn women into his dream girl - a drow hottie with incredible regeneration abilities. Yep, you guessed it. He accidentally received an injection. In addition, just to rub it in, the amazing regeneration means he can't find a way to turn back to his old self.
Power mimic Counterpoint has this happen to him more than once in the Whateley Universe. In a holographic simulation, the version of Counterpoint attacks Phase to steal Phase's powers; but Phase figures out how to use his density-changing powers to kill someone with density-changing powers. Counterpoint beats up Chaka to get Chaka's Ki-manipulation power; but Counterpoint can't use both yin and yang (he's a very masculine god of war) and so the built-up yin in his system nearly kills him before Chaka saves him. And then he tangles with Jobe...
In the College Humorspoof of Inglourious Basterds, Nazi colonel Hans Landa is an extreme stickler for grammar who becomes increasingly frustrated with Monsieur La Padite's grammatical errors and unwillingness to cooperate with him. Triumphant with his discovery that there are Jews hiding under La Padite's floorboards, Landa mistakenly utters a dangling participle and chooses to commit suicide out of shame.
Ink City: Trevor plotted to paralyzeYakko and Rigby so he could experiment on them. Instead, he wound up trapped within his own paralyzing fluid. Rigby then broadcast a video of this latest kidnapping attempt to the City at large as proof of Trevor's nature; Trevor had previously used a video of Rigby attacking him to damage his friendship with Phoenix and paint himself as the victim.
Goodbye Kitty: Black Kitty's deaths are often caused by this.
Season 6 of Arby 'n' the Chief introduces the character, Justin. Revealed to be the mastermind behind the console banning hacks that Arbiter, Master Chief, Chaos Theosis and Trent Donnovich have been using in seasons 5 and 6. When Justin presents Trent with network crippling software, guess who Arbiter takes out first?
In one episode of Rooster Teeth's "Things to do in Minecraft", Geoff and Gavin create the Hop Till You Drop maze and takes glee in watching the other Rooster Teeth members falling into the lava pit below. Flash forward to "Let's PlayMinecraft" episode 44 and Geoff is the first one to find and mine the Tower of Pimps. A bad step causes Geoff to throw an Ender Pearl wildly. Where does it land? The lava pit, taking him out AND losing the Tower, forcing them to redo it over again.
In chapter 5 of the Neopian Times story Revenge, during a Yooyuball game, Alex uses her sling to hurl a potion at Naqasa that will turn her into a hideous mutant Usul. However, Naqasa's brother Q'tai is also playing and throws his ball to hit the potion and send it flying in Alex's direction so that she gets drenched with it instead.