- AFK: Serena is a healer and overall nice person, though when Clint pushes her too far, she nearly kills him with a sudden spell which causes an airless void to form around his head.
- While nice characters are few and far between in AJCO, the ones that are there should almost certainly be feared. Possibly because they're such a rare breed.
- Kaja is motherly and forgiving, taking good care of her cheerful cherry-blossom town on the water with all the love one would expect. She's also a centuries-old former Knight Templar angel sworn to protect whoever asks for her help, and reveals her true form to A_J in a fit of anger when Egg is sentenced to death.
- Blue is normally sweet, fluffy and utterly docile - so nice, in fact, that even Krauzer has a soft spot for her. When a Blood Moon rises, however...
- Mei is clumsy, friendly and permanently well-meaning, though as a zombie she can and possibly will tear her enemies limb from limb should they push her that far. She's practically indestrucible.
- The Annoying Orange: It pays not to anger Marshmallow, even the title character warns about this, through Grapefruit found this out the hard way.
- In the web serial Ash & Cinders, Cinder first stands up for herself when she threatens to kill the Forest Queen and the rest of her kingdom if they refuse to give her her brother back.
- In Ask King Sombra: Caribbean Splash is probably one of the cheeriest ponies you could meet. Then his best friend was killed during the attempt to escape from the Crystal Wolves. Sombra says he and the other deaths of the battle don't matter due to being, to put it nicely, a self-centered D-bag. Splash overhears this and decks Sombra right in the face, hard enough to draw blood, followed by giving him a What the Hell, Hero? in a complete rage and trying to beat the hell out of him.
- 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 Stalker with a Crush Alex interferes and refuses to be ignored.
- Carmilla: Laura Hollis, All-Loving Hero, truly wants to save everyone possible at her Crapsack World Academy of Adventure. She's an upbeat, eager Determinator, who will withstand utter hell if it will keep people safe. But if you push her too far, she will break... and chances are very good that you will not survive. When she crosses her Despair Event Horizon in season two she flat out kills Vordenberg, and then there's her actually ordering Carmilla to kill the cannibal baker in the Christmas Special...
- Chakats from Chakona Space 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...
- Beware Chester Cheetah.
- Daisy Brown is generally a sweet and innocent girl, but a few times, she snaps and gets angry with Alan. In Artistic video, it's implied she hits him just offscreen. In "the basement" she actually stands up to him and even dares him to kill her before mocking him when he doesn't.
- Alfred, the massive construction worker from Darwin's Soldiers, 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 Super Strength is extremely stupid. His most extreme case was when he got so angry that he threatened to dismember someone and beat them to death with their own limbs. And if Dr. Zanasiu hadn't calmed him down, there was no doubt he would have done so.
- Mirielle from Dawn of a New Age: Oldport Blues is a sweet girl who's been raised by Sickeningly Sweethearts to be as kind and generous to others as possible. However, she's also shown to have a sharp-tongued, vindictive side that comes out against people she doesn't like. Barbra mentions in passing that she doesn't think anyone would want to cross Mirielle.
- In Dead West, Gervas, the narrator is a Kind Hearted Cat Lover, and a perfect gentleman. Cross him, and expect to be pulverized. The Porcelain Doctor is this combined with Beware the Quiet Ones; he is the sweetest, most polite, meek Bishounen in dainty glasses and always dressed sharply. But if you press a Berserk Button, prepare to die. The effect is more shocking since his aura will make you look at him like the most fragile and precious little thing in the world.
- Donnie DuPre from Demo Reel is adorably useless, cuddly and a total moeblob, but he's steely and vicious when it comes to Hollywood. For a damn good reason too.
- Usually, Doki is the nicest person in the world but you better not insult her fighting skills or you'll look like this.
- The eponymous doctor in 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...
- Dragon Ball Z Abridged:
- Gohan's adherence to this trope is parodied. When he is a shy, meek, nerdy kid with good manners, a lot of the characters in the series abuse him in hilarious manners. When he loses it (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: FUCK THE STREAM!
[Kicks Dodoria into a house.]
- After numerous battles and watching his idiot father get himself in and out of world-shattering duels, Gohan matures and solidifies his pacifist nature... until he encounters Cell, who cannot be reasoned with or defeated by his father. After numerous threats, taunts, and a good "The Reason You Suck" Speech by Android 16, Gohan's psyche breaks and goes into Super Saiyan 2, with no threats or snarks, just Tranquil Fury.
- Gohan's adherence to this trope is parodied. When he is a shy, meek, nerdy kid with good manners, a lot of the characters in the series abuse him in hilarious manners. When he loses it (And you'll know it when he does), it's a sign that someone is going to get hurt.
- In Endless Saturdays, 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.
- The Guild:
- Codex is shy and accommodating to the point of being an Extreme Doormat, 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 very creepy, but always sweet and giving, to the point of people 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, 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 Gungan Council. 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.
- Hero House has Nightwing. He may be friendly and slightly pathetic, but when push comes to shove, he can stand toe-to-toe with Predators twice his size.
- Jay from Marble Hornets. He is a normal, nice guy who tries to find out what goes on around him and his friends, but if, say, The Operator does stuff like threaten Jessica, he will tackle and wrestle him, even if it gives him 7 months of Laser-Guided Amnesia.
- Mr. X in Resident Evil 2 Abridged is given a heaping helping of Adaptational Heroism, wanting nothing more than to befriend Leon as soon as he sees him. Unfortunately, Mr. X's monstrous appearance scares Leon so badly that he shoots him on sight, which Mr. X repays accordingly, but he doesn't become truly pissed until after being dunked in liquid metal.
- The Saga of Tuck has several perfectly nice, ordinary characters who are all but trained covert operatives in intelligence, counterintelligence, black propaganda and sabotage.
- SCP Foundation: Even the sweetest, most adorable SCPs can display this.
- One of them is a pair of sentient fishing trawlers that act like Sickeningly Sweethearts. 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 sentient tank that 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 harmless hitchhiking ghost. It will... come back to haunt you.
- Another is a 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.
- 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.
- In Super Powereds, hurting people Vince cares about is a very bad idea. Best exemplified at the end of Year 2, when he has a vision of a girl from his past dying and goes on a rampage, and near the end of Year 3 when Sasha dies and he goes to kill the man who did it.
- Survival of the Fittest is perhaps one of the most perfect environments for turning nice guys/girls into murderous psychopaths.
- One of the most jarring examples is 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 Maria Graham, a happy-go-lucky Cloud Cuckoolander who was rendered almost catatonic for days after being beaten half to death and accidentally setting someone on fire trying to escape. However, after watching 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.
- 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.
- Matt of Two Best Friends Play is usually the calmer of the two friends, preferring Lighter and Softer games. But when he plays Deus Ex: Human Revolution, after some initial reluctance, Matt goes nuts with the Videogame Cruelty Potential, stabbing and punching all the NPCs he can find.
- When Dio kicks Danny in the Vaguely Recalling JoJo series, Jonathan mercilessly pummels Dio. Dio receives the same fate when he accidentally kicks Danny into the incinerator.
- Whateley Universe:
- Jade Sinclair (Generator) qualifies. Normally the cute, shy, wacky 'little sister' figure, when she's 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. 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 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. Hell, throw in Aquerna and Dragonrider while you're at it, as they've both been shown to bring the whoopass when needed.
- Folder once seriously hurt a close friend with his powers, and he swore to never use violence for anything again, ever. Fortunately for the bullies, he stuck to this. Unfortunately, they didn't see the intense rage he was keeping buried. The result when she was finally pushed to far was purest Nightmare Fuel.
- Skitter from Worm is in many ways the nicest of the Undersiders, a group of villains trying to take over Brockton Bay and will go to any lengths for those she takes under her protection, even for complete strangers. She's also the most powerful, dangerous and terrifying of the group, despite it containing darkness manipulators and a girl with an army of monster dogs. This is because she wants to use her power for good and has resolved to make full use of intimidation to scare people into submission rather than harming them and, failing that, is prepared to use brutal combat pragmatism to take down stronger threats that herself as quickly as possible.
- In Wrestle Wrestle April admits she has a timid voice, but Spoony points out that when she's pissed, her voice is booming, such as a Big "WHAT?!" she did watching a show.
Beware The Nice Ones / Web Original