* TheAnnoyingOrange: It pays not to anger Marshmallow, even the title character warns about this, through Grapefruit found this [[https://www.youtube.com/watch?v=56SA_C9o9VU out the hard way]].
* Gohan's adherence to this trope is parodied in ''WebVideo/DragonBallZAbridged''. When he is a shy, meek, nerdy kid with good manners, a lot of the characters in the series abuse him in hiarious manners. When he loses it ([[PrecisionFStrike And you'll know it when he does]]), it's a sign that someone is going to get hurt.
-->* After Dende's Father and Brother are killed.*
-->'''Krillin:''' Breathe Gohan! You're a leaf. A leaf in a calm stream!
-->'''Gohan:''' '''[[PrecisionFStrike FUCK THE STREAM!]]'''
-->* Kicks Dodoria into a house.*
* Codex of ''TheGuild'' is shy and accommodating to the point of being an ExtremeDoormat, but when she found out her boyfriend had dumped her for another man she set fire to his cello.
** Lampshaded in Season 3 by Vork: "Codex, you of all people turning on me as well? Do I truly have the power to snap your gentle spirit?"
** Zaboo is [[StalkerWithaCrush very creepy]], but always sweet and giving, to the point of people [[MisaimedFandom wondering why Codex doesn't want to date him.]] And then he goes crazy on Valkyrie. Codex, whose plan it was to go after Valkyrie in the first place, says, "Ok, he's basically freaking both of us out now."
** Clara was the other nice one of the guild. She was a sweet, [[CloudCuckooLander if slightly out there]], overgrown teenager who...tried to be a good mother. Probably. Then Vork didn't give her the orb, so she spent the next few days killing him nonstop.
* ''{{The Saga of Tuck}}'' has several perfectly nice, ordinary characters who are all but trained covert operatives in intelligence, counterintelligence, black propaganda and sabotage.
* Among many in the FFRP forum The Town/Acronymia, Pesty. A cute combination of Genki and Cloud Cuckoolander catgirl. She adores her boyfriend Grant, their adopted daughter Pixie, and lots of other people. When Grant's crazy and evil side tries to take him over, she snaps him out of it by bitch-slapping him and shouting in his face. In a future-possibility-what-if plot thread, the kidnapper of Pesty's grandson earns him an utterly nightmarish end.
* In the WhateleyUniverse, Jade Sinclair (Generator) qualifies. Normally the cute, shy, wacky 'little sister' figure, when she's [[BreakTheCutie pushed too hard]] one day, and then attacked by Bloodwolf (an avatar of the werewolf spirit) and two fellow Ultraviolents, she snaps. Bloodwolf ends up nailed to a tree. ''With railroad spikes.''
** Lately she seems to be actively considering a potential career as the Psycho Babysitter From Hell -- perfectly harmless to her future charges, but woe to whoever thinks to threaten them.
** It bears mentioning that, of those among her circle of friends who have killed other people (which include a terrifyingly powerful mage, a girl who wields a sword that can cut through anything, a soul-eating demon and ''[[PersonOfMassDestruction Tennyo The Motherfucking Destroyer]]''), Jade's kill count exceeds the rest ''combined'' by a factor of four. At the very least.
** Speaking of which, Tennyo herself is a very kind, if somewhat somber, person who spends a lot of time worrying about accidentally hurting others with her powers. Considering how powerful she is, she has good reason to worry, so it is generally considered a ''very'' bad idea to give her a reason not to care about this.
** In fact, let's put the entirety of Team Kimba, plus Carmilla, on the list.
* [[ChakonaSpace Chakats]] are usually nice to a fault -- empathic, social, family-oriented, and almost too good to be true except that they normally actually are; their designers did a good job. ''Don't'', however, threaten one's cubs or even hir best friends and family will have trouble keeping hir from shredding you on the spot...
* Alfred, the [[TheBigGuy massive]] construction worker from ''DarwinsSoldiers'', is explicitly described as not "the kind of person to pick fights". And it takes a lot to provoke him into physical action. But anger him enough and you'll see why angering someone with SuperStrength is ''[[TemptingFate extremely]]'' [[TooDumbToLive stupid]]. His most extreme case was when he got so angry that he threatened ''to dismember someone and beat them to death [[GrievousHarmWithABody with their own limbs]]''. And if [[TheHero Dr. Zanasiu]] hadn't calmed him down, there was no doubt he would have done so.
* The eponymous doctor in [[WebVideo/DoctorHorriblesSingalongBlog Dr. Horrible's Sing-Along Blog]]. Despite being a supervillain, he wouldn't dare think about murder or fight in a park with kids. Then Captain Hammer talked about doing Penny...
* ''WebVideo/{{Awkward}}'' gives us Lester, a wonderfully amiable and somewhat put-upon hero who will put up with quite a lot -- until he actually seems to be making progress with Steph, and his live-in StalkerWithACrush Alex interferes and refuses to be ignored.
* SurvivalOfTheFittest is perhaps one of the most perfect environments for turning nice guys/girls into murderous psychopaths. Perhaps one of the most jarring recent examples being Liam Brooks in v4, originally a rather quiet character with a love for gardening and a phobia of blood, but after the death of his girlfriend he dove headfirst onto the crazy train, putting together a makeshift garden with said girlfriend at the center while he proceeded to brutally kill three people and injure a third trying to add more bodies to it.
** A lesser example in v4 would be [[GenkiGirl Maria Graham]], a happy-go-lucky CloudCuckoolander who [[HeroicBSOD was rendered almost catatonic for days]] after being beaten half to death and accidentally setting someone on fire trying to escape. However, after watching [[EvilBrit Maxwell Lombardi]] kill the boy she was in love with and her best friend, one after the other, and then try to kill her while mocking the former, she finally snapped hard and the two ended up viciously beating on each other in a burning building.
* Matt of ''WebVideo/TwoBestFriendsPlay'' is usually the calmer of the two friends, preferring LighterAndSofter games. But when he plays ''VideoGame/DeusExHumanRevolution'', after some initial reluctance, Matt goes nuts with the VideogameCrueltyPotential, stabbing and punching all the [=NPCs=] he can find.
* ''TheGunganCouncil''. Io Akima seems to be one of the most lovable, playful persons around. That is, until Adira smashed her datapad, which was a gift from a friend that had died. Cue Io going from wanting to tease Adira to outright attempting to murder her.
* The title character of ''Erika's New Perfume'' is normally a loving, soft spoken ShrinkingViolet, but when [[BigBrotherBully Big Sister Bully]] Marie tries to [[spoiler:reverse [[CoolBigSis Sarah's]] PlotRelevantAgeUp,]] she ''snaps'' and lays into her with an epic combination TheReasonYouSuckSpeech / WorldOfCardboardSpeech that leaves her flabbergasted. In a ''wet diaper,'' no less.
* Beware [[http://www.youtube.com/watch?v=A8Z-JCP4Q6A Chester Cheetah]].
* In ''WebAnimation/DeathBattle'', between two combatants, if one of them is nice and the other pretty much isn't, the nice one usually ends up winning.
** [[WesternAnimation/MyLittlePonyFriendshipIsMagic Rainbow Dash]] ''only'' attacks [[Franchise/TransformersGeneration1 Starscream]] when he threatens to kill her, [[spoiler:then delivers a [[CurbStompBattle thorough beating]]. Then, she '''[[YourSoulIsMine eats]]''' his [[OurSoulsAreDifferent Spark]]!]]
** [[VideoGame/YoshisIsland Yoshi]] is described in the intro as a "cute, happy dinosaur". [[spoiler:His fight with [[VideoGame/KillerInstinct Riptor]] ends with him throwing the ferocious fighter over a cliff, after drenching the latter's face [[HoistByHIsOwnPetard in his own acid]].]]
*** This one is particularly notable as for most of the fight, Yoshi just stands there getting beat up.
** [[Franchise/SuperMarioBros Princess Peach]], the somewhat ditsy, happy-go-lucky girl who can't take ten steps without getting kidnapped, [[spoiler:kicks [[Franchise/TheLegendOfZelda Zelda's]] face so hard [[YourHeadAsplode her head explodes]].]]
** And then there's the loud-mouthed, fun-loving {{Spider-Man}} [[spoiler:slingshot-kicking Franchise/{{Batman}}'s torso off?]]
* Usually, Doki is the nicest person in the world but you better not [[http://akaichounokoe.deviantart.com/gallery/?q=crippled+girl#/d59elny insult her fighting skills]] or you'll look like [[http://akaichounokoe.deviantart.com/gallery/?q=crippled+girl#/d4qzfti this]].
* Donnie [=DuPre=] from WebVideo/DemoReel is adorably useless, cuddly and a total {{moe}}blob, but he's steely and vicious when it comes to Hollywood. For a [[HorribleHollywood damn]] [[MissingMom good]] [[DrivenToSuicide reason]] too.
* ''Wiki/SCPFoundation'': Even the sweetest, most adorable [=SCPs=] can display this. Just to put an example, one of them's [[http://www.scp-wiki.net/scp-1522 a pair of sentient fishing trawlers]] that act like SickeninglySweethearts. What happens when another ship attacked one of them? The other ''rammed it at Mach 4''. Not even the lifeboats made it.
** Another is a [[http://www.scp-wiki.net/scp-516 sentient tank]] that [[IAmNotAGun turned to pacifism]]. It will still open fire on traitors to its homeland, and on anyone who harms a civilian within its vicinity.
** Do not attempt to decommission a [[BewareOfHitchhikingGhosts harmless hitchhiking ghost]]. It will... [[http://scp-wiki.wikidot.com/scp-1337 come back to haunt you]].
** Another is a [[http://scp-wiki.wikidot.com/scp-054 sentient mass of water that takes the form of a woman]]. She was nice and friendly to male staff, but the experiments performed on her by them traumatized her so much, she finally had enough and lashed out at them which temporarily changed her object class to Euclid.
** [[http://www.scp-wiki.net/scp-1609 SCP-1609]] used to be a perfectly harmless chair that would teleport behind you if you needed a seat. One botched decommission by woodchipper later, it's taken to teleporting its remaining splinters into people's lungs if it feels threatened.
* When Dio kicks Danny in the ''WebVideo/VaguelyRecallingJoJo series'', Jonathan mercilessly pummels Dio. Dio receives the same fate when he accidentally kicks Danny into the incinerator.
* In Blog/AskKingSombra: Caribbean Splash is probably one of the cheeriest ponies you could meet. [[spoiler:Then [[http://ask-king-sombra.tumblr.com/post/51259196758/their-song-is-whistle-a-happy-tune-from-the-king his best friend was killed during the attempt to escape from the Crystal Wolves.]] Sombra [[KickTheDog says he and the other deaths of the battle don't matter]] due to being, to put it nicely, [[ItsAllAboutMe a self-centered D-bag]].]] Splash overhears this and [[spoiler:[[http://ask-king-sombra.tumblr.com/post/51840622066/caribbean-puuuuuuuuuuuuuuuuuuuuunch decks Sombra right in the face]], hard enough to draw blood, [[http://ask-king-sombra.tumblr.com/post/52099130841/splash-sombra-wat-r-u-doin-splash-sombra followed by giving him]] a WhatTheHellHero in a complete rage and trying to beat the hell out of him.]]
* In ''EndlessSaturdays'', Kara, while perhaps the most quiet and normal of the three, gets annoyed enough by her siblings to try and ensure that they get permanently lost in the wilderness.