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.
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.
Asuka Quest: SB!Asuka is far nicer than her canon counterpart. She's also a far scarier fighter in her Evangelion due to her creativity and knowledge of physics, to the point where the Angels had to massively buff themselves just to stand a chance against her. Among her tricks include one capable of destroying planets and one theorized to be a Reality-Breaking Paradox (currently only tried in simulators).
The Awkward Compilation 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 WorldAcademy 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 orderingCarmilla 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...
Critical Role: Caduceus Clay is easily the kindest member of the Mighty Nein, and most often the one the rest of them turn to for comfort and guidance. He also rarely deals any actual hits when the Nein get into fights, instead focusing more on buffing and healing his teammates, and prefers to try and talk things out before resorting to violence. That is, unless you hurt his friends or his home. When Fjord is killed by an agent of Uk'otoa, Caduceus flies off the handle and starts unleashing the vilest of necrotic spells, and when the Nein encounter Caleb's abuser, Caduceus is one of the first to suggest they kill him then and there. He's also far from harmless even when he isn't angry, as his primary method of protecting himself is to summon a swarm of flesh-eating insects that start devouring anyone who gets close.
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 extremelystupid. 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 make him angry, 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 damngoodreason too.
The Thistlesprings are arguably the kindest, least cynical family among the Bad Kids, but the parents put up arguably one of the better fights against the big bad’s assassination attempt with an automated army and a tank. And that’s not getting in to their son, who is a sweet, sensitive, and considerate…path of the berserker barbarian.
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...
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.
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.
Greg, the titular Epic NPC Man, is a nice garlic farmer, who greets adventurers and gives quests. In one episode an adventurer keeps skipping Greg's dialog and Greg snaps, pulls a knife and threatens him with death unless he listens to all of it.
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.
Any Protectors of the Plot Continuum agent who has a sweet and friendly demeanor will inevitably become a terror to Suvian entities, as agents' jobs include assassinating Mary Sues, performing exorcisms (which involve bashing the possessed character over the head) or similar violent or semi-violent duties.
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.
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.
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 (performed by the Global Occult Coalition) later, it's taken to teleporting its remaining splinters into people's lungs if it feels threatened.
The notoriously amoral SCP Foundation has an Ethics Committee. In-Universe, it's mostly seen as nonexistent or a joke. It's not. The Ethics Committee are responsible for making damn sure that even with all the horrors they work with, the Foundation never crosses the line. To that end, they have the highest security clearance and can (and in some cases, have) order the O5 council killed if they go too far. All the horrific things the Foundation does to keep containment? That's not stuff the Ethics Committee couldn't stop, that's stuff the Ethics Committee explicitly signed off on because they determined that the consequences of the SCPs being uncontained were even worse than whatever the Foundation does to contain them. Yes, even Procedure 110-Montauk.
To balance the costs, we must know the costs.
The Three Moons Initiative is generally benevolent and its interventions on Earth are mostly for humanitarian purposes... but they have multiversal influence, advanced technology, and zero hesitation of using brutal force against people who abuse their authority against their fellow humans.
SCP-2578-D (e-mail sent to targets): I never miss my mark. Abdicate and you will live.
Sorted Food: James is a kind, gentle and shy-seeming individual, who carries himself with an almost childlike innocence. He also holds black belts in multiple martial arts, and at one point effortlessly disarmed a knife-wielding Barry while complaining about how he was making a fuss in the kitchen.
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.
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.
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.
The Whateley student classification system has a few variants on the 'Ultraviolent Armband', Color-Coded for Your Convenience of course, and they run the gamut: on the one hand, you have the students who are actively violent and only kept at Whateley because A. the more people know about them, the easier they'll be able to take down, and B. better there than on the streets. You get the Pacifists, like Folder. And then you have the unwilling ragers, who are saddled with a "Thou Shalt Not Provoke" edict. A lot of them, like Razorback, are perfectly nice, if a little on edge or a bit depressed now and then. If, however, you ignore that ruling, you may wind up with a feral dinosaur able to casually dismember you and everyone in a 100-foot radius.
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.
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