Beware the Nice Ones/Anime and Manga

"Matsuda:"
 * Belldandy from Ah! My Goddess is a prime candidate, with her always presenting a quiet and gentle personality. Because she has such incredible self-control and such a kind personality, she's given access to more power than anyone else in the series, with the exception of Hild (and the Almighty, but he doesn't appear).
 * When her self control slips, nearby glass shatters and pipes burst. Seeing a pattern, Urd exploits Belldandy's jealousy, which makes Belldandy subconsciously create an explosion so powerful it defeats Garm, who outclassed Urd.
 * When they're at the hot springs with the demon Mara, Belldandy lays down a rule against fighting. "And if you break it, I will punish you." Urd and Mara are understandably unnerved.
 * And God save your soul if you dare to hurt Keiichi. She's scary enough when she's just disappointed in your actions... this will flat-out make her angry. The first time this happens in the manga, she does not hesitate to unleash her "Holy Wind Press", an attack spell, on his assailants, a sight which absolutely terrifies Skuld.
 * Recently, she
 * Seriously, Bell-chan is a rather bossy girl by nature. Her sisters are even a little afraid of her. She is just really, REALLY good at covering it up with her obedient facade. If she wanted, she could make Keiichi do absolutely anything. Thank the allmighty she's the nicest person you will ever meet.
 * Speaking of Valkyries, Lind is a polite and proper girl with the kind of decorum you would expect of an Officer and a Gentleman. Her job description? Heaven's Own One-Man Army.
 * Monster Rancher Golem is as gentle a giant as you could wish for and only really fights because he has no choice....but piss him off and it is.
 * Genki might count too, it never really happened in-show, but we are talking about an innocent-looking eleven-year old who regularly kicks genetically engineered dinosaurs, Living Weapons, and robotic stone dragons in the face and will headbutt anything. If he ever really lost it his general abilities,, suggest he would go absolutely Super Saiyan on everyone and thing in his way.
 * from Black Butler. Through most of the Jack the Ripper arc, he's the quiet/suicidal/klutzy companion of who more or less functions as comic relief through his epic failure at his work. Until you catch him, of course. Then he pulls a grin that can be nightmare-inducing at best, proceeds to change his appearance dramatically and turns into a chainsaw-wielding psychopath that is very forward about his creepy attraction to Sebastian, within the same five minutes talking about both wanting to cut him into pieces and bearing his child.  He helps  kill the prostitutes because it's a distraction and he's bored with sticking to his list.
 * Then there are the, klutzy, bumbling, carefree, and happy. Then the circus comes to town and we learn why they have the jobs they do.
 * Especially in the manga, the last person you would expect to preform a cold grizzly murder of a man while his friends watch in horror.
 * Motoko Gettou is a double instance. If you mess with her, you get beaten up by one of her split personalities, of which there are three; each with its own individual conscience and each as badass as the next. Assuming you somehow manage to beat those, enjoy it while it lasts;
 * Baccano! seems to like this trope a lot: many of the characters come across as very amiable individuals—that is, until you push them too far. For example:
 * wasn't planning to kill you—no, siree. All he wanted to do was conduct his train, ogle that cute girl in the first class car, and tell silly ghost stories to pass the time. But no, you just had bring this whole "train hijacking" thing into this. And Tony—did you really have to kill Tony? What did he ever do to you? Oh well, it's too late now. He's just gonna have to teach you a lesson now. A very painful, bloody lesson...
 * In the Light Novels, Eve Genoard also enacts this trope. When brags to her that he killed her father and oldest brother, she almost immediately casts aside her status as The Ingenue, picks up a dropped revolver, and tries to blow his head off.
 * She shows signs of this in the anime as well, when she escapes from the Runoratas by tying one of them up, and possibly knocking him out as well.
 * The anime example doesn't really count, as the "Runorata" who was tied up was actually a spy and a good guy, and it's heavily implied (really all but outright stated) that he let her go and tied himself up.
 * Bleach:
 * Captain Retsu Unohana. A motherly Yamato Nadeshiko type in charge of a company full of healers, one look from her can scare anyone. Even people who don't scare easily such as Kenpachi.
 * Gentle Giant Hachigen Ushoda manages to stay calm and polite even when he reveals himself to be.
 * Handsome Gentle Giant Chad who refuses to harm even bullies, but don't ever threaten his friends.
 * One Piece: Monkey D. Luffy is generally a happy-go-lucky guy, and very cheerful...until you hurt his True Companions, or his friends... or your True Companions. Heaven help you if you do. It's about the only time that he ever takes off his Nice Hat.
 * Luffy's not the only Straw Hat that qualifies. Witness, Tony Tony Chopper the hyper-cute reindeer doctor, cute, innocent and cuddly one moment but make sure your will is updated before you decide to do something stupid like make him mad.
 * This can qualify for all the Straw Hat Pirates, not just Luffy and Chopper; in spite of them being one of the most notorious crews in the world, they're all kindhearted and they never throw the first punch. But provoking them too much is comparable to digging your own grave; each member of the crew could effortlessly and singlehandedly take out an army, and they would declare war on the entire world for the sake of just one of their friends.
 * Special mention should go to Conis, a sweet girl from Skypeia who was introduced as a Proper Lady-type character. After learning that her country's psychotic God-like ruler intended to destroy Sky Island and everyone on it and watching her father  get killed by said ruler, she ends up driving a ship into the Sky Guards, facing down an angry mob that refuse to believe her, threatening the Sky Guards with a bazooka, and publicly shouting heresy to convince them that their god has abandoned them.
 * In Black Lagoon, Rock is by far the nicest person you will find... but if you push him TOO far,  he will show you that he is just as dangerous as his crewmates.
 * And the female employees of the Lovelace family are also not to be trifled with, despite their demure and deferential exteriors. Especially Roberta. Lay a finger on the Young Master and she will kill you.
 * Hayate Yagami from Magical Girl Lyrical Nanoha is the master of a dangerous book that her guardians want to complete, as well as a sweet and caring girl that wouldn't hurt anyone. You can see where this is going. It does take a massive gambit to both give her the power to do this and a reason to snap, but snap she does.
 * Then we have Nanoha herself, whose sweet and innocent persona distracts from the fact that she has the power of a Physical God. Her favorite method of making friends seems to be beating them to near death and asking questions while she does it. And heaven help you if she actually gets angry. The oft-cited example of her blasting Teana to smithereens ("Shall I... cool your head a little?") for disappointing her doesn't even come close to receiving her real wrath, which involves being on the receiving end of an Earthshattering Kaboom. From across a battleship, if she has to. On a side note, Nanoha's blasting of Teana wasn't so much carried out of disappointment, but as a lesson to show her that shooting magic (in which both of them specialize) hurts like a bitch.
 * And the battle nuns of the Saint Church, who can go from caring nurse to hard-boiled soldier in a matter of seconds.
 * Most of Riot Force 6's combatants are generally nice people that have combat capability equal with (at least) heavy artillery. And they can be really, really scary when they snap out.
 * Especially Caro Lu Rushe. A gentle, big eyed, shy little girl, a B Class mage specialising in buff spells, what could she possibly do? Piss her off enough so she actually taps into her summoning magic and run for your Super Robot, because whatever she summons would be more than appropriate to fight it. That said, your Super Robot needs to be large to even stand a chance...
 * Subaru Nakajima is known as "Gaogaigar-tan" for the enormous number of shout outs in her combat style, . Her berserker moment brought upon . would be a Crowning Moment of Awesome if it weren't so damn terrifying is SO SCARY IT'S AWESOME. "Give...her...BACK!"
 * Similar to Bleach's Unohana, Shamal is typically kind, polite and soft-spoken, but when she gets angry, even Nanoha is scared of her. This could be because the first time Nanoha encountered Shamal, she managed to use teleportation magic to steal Nanoha's Linker Core from afar, rendering her unconscious.
 * Let's put this in perspective. She literally reached into Nanoha from a mile away, and effectively ripped out the core of her magic. And the scary part is, when they do that, there doesn't seem to be any counter to it.
 * Touma from the Force manga also qualifies in the most recent chapter. He's shown himself to be dangerous, but not in control of the power of his Divider through most of the manga, but when the TSAB forces attack the Huckbein airship, resulting in a massive melee between the bloodthirsty Huckbein and the reconstituted Riot Force 6. The resulting carnage and the threat of his friends getting caught in the crossfire pushes Touma almost over the Despair Event Horizon Perhaps even more terrifying is Touma's lines just before this happens, showing just how far he's been pushed.
 * The original Reinforce comes across as pretty Extreme Doormat most of the time, soft-spoken and obedient. The sound stages reveal that she is willing to let Hayate grope her breasts, and is willing to try to reach out and show kindness to Vita in spite of the latter's temper and angry rejections of her attempts. Reinforce very nearly destroyed the Earth because someone decided to greatly upset Hayate.
 * We also have another Hayate, this time the eponymous Hayate the Combat Butler who does this in both the anime and the manga whenever Nagi gets kidnapped. First during the first episode and more comically when he takes down a giant mecha with an machine gun.
 * Maria certainly qualifies, arguably in a greater extent. Just say something about her age.
 * The narrator is afraid of her!
 * Let us clarify: The narrator, which is voiced by Norio Wakamoto, is scared of her. let that sink in for a minute....
 * When Nausicaa's father King Jhil dies in Nausicaa of the Valley of the Wind, the kind-hearted princess becomes a murderous embodiment of berserker rage who appears to revel in slaughtering the enemy (one man in the manga, an entire squad in anime) until Yupa stops her. Afterwards, though, she is devastated by the thought that her heart could contain such rage.
 * That's only in the movie. In the original manga, what sets her off is the Torumekians landing in the Valley without permission or quarantine (contaminating the Valley's crops and trees), having their knights attempt to pick a fight, defiling a grave Nausicaa dug, and bringing Worm-handlers into the Valley, whose slugs - attracted by the scent of the trinket Nausicaa is hiding - slither up her body. The result of her snapping is the same, though.
 * For the record, Jhil dies of natural causes almost halfway into the story, long after Nausicaa leaves the Valley; she doesn't even find out until near the end.
 * In a flashback, we see Kaede Fuyou from SHUFFLE! go off the deep end on the male lead after her mother's death (Boxcutter Kaede), an effect that is repeated near the end of the series when the lead starts seriously going out with another girl. Kaede and the lead, Rin, have effectively been living as husband and wife for close to ten years, which can be seen as Kaede trying to repair the damage her other self caused to Rin.
 * My-HiME positively ADORES this trope:
 * Polite and graceful Schoolgirl Lesbian Shizuru Fujino had been nothing but kind and supportive to her best friend and object of her affections, Natsuki Kuga, for half of the show. Near the end, though, that same love made her evil, sending her on a rampage to eliminate anyone who came between her and Natsuki. Shizuru's fandom remained loyal, though irritated that the writers went a cliched route, and because it happened so close to the end of the series to have any real emotional impact. Consider for a moment that she gets so depressed that she kills herself in the Dating Sim based on the anime if the protagonist decides to wind up with Natsuki, and the previous event may not seem quite as ridiculous. Her popularity possibly gives her ending a note of hope, though, as well as a more sympathetic role in Mai-Otome.
 * Killing herself over unrequited love doesn't necessarily serve as an indicator of willingness to kill other people over anything from actual threats to mere insults against Natsuki. Considering that Shizuru, in the dating sim, also, the character may be different in that case, and there's more at play.
 * Similarly, the normally bubbly and cheerful Shiho Munakata lets her jealousy overcome her sanity, eventually leading to a showdown with the female lead Mai.
 * Oh, and Reito Kanzaki? Mai's other love interest? The soft-spoken guy who wears all black? One Post Episode Trailer has Nagi lampshade this by saying something like "Come on...you mean to tell me he didn't seem suspicious from the start?"
 * Hell, Mai herself went into snap-out mode when she learned that . When you see her biting her lip and drawing blood, you know you screwed up big time.
 * Don't forget Wataru Ishigami, Sister Yukariko's controversial love interest. One of his earlier apparitions had him dorkily spinning around Mai's brother Takumi and begging him to be his model for his next painting...
 * In the manga, Takumi, Mai's sickly younger brother who's typically soft-spoken and considerate,.
 * Joked around with in Mahoraba because it has two such characters. The first is Tamami who has her eyes closed and generally acts nefarious to the protagonist and to others. The second is the protagonist's teacher, Shirogane-sensei, who throws bad students into "the Closet".
 * Saki, one of Kozue's alternate personalities, could arguably apply, though she wouldn't necessarily become a threat to health and sanity. Her Break the Cutie threshold is insanely low.
 * Explicitly parodied in Ranma ½: when the family is convinced the normally serene and placid Kasumi has finally snapped after they thoughtlessly go out to dinner without her and return to find evidence of a major psychotic tantrum. They're on the verge of "sacrificing" Ranma to appease her anger when it turns out the damage was all from Kasumi's attempts to capture a cat that had gotten into the house.
 * Used straight in the "Evil Ogre" Manga arc and "Faster, Kasumi! Kill, kill!" OAV: When Kasumi is possessed by a vengeful ogre that makes its host act on their "most evil desires" everyone is terrified by the possibilities as she sweetly goes about adding little evil twists to her normal daily routines. Fortunately Kasumi's most evil desires don't extend much beyond spreading tacks in her father's bedding, embroidering "Okama" ("queer") on the back of Ranma's shirt, ordering tons of expensive takeout food inappropriately early in the morning and cutting cloth dolls out of the sheets.
 * Fanfic writers seem to like this trope in regards to Kasumi.
 * Ranma's mother Nodoka Saotome is a rather nasty swing on this trope. She's a kindly, sweet woman whom both Ranma and Akane look up to, with the latter being implied to consider her almost a substitute mother... however, she is even more prone to put Honour Before Reason than any of the other cast members. Even though the Seppuku pledge her husband made is so vague that nobody else would even consider it to be worth the paper it was scrawled on, she's so devoted to it that she carries a sword everywhere she goes, just in case she meets Ranma and she decides he's unmanly. And that means everywhere- she's even shown sleeping and bathing with it. And it doesn't exactly take much for her to start pulling it out, either.
 * Ranma himself, despite being a jerk can fall into this category. Under normal circumstances, Ranma is a rather cynical, reserved un-socialized jerk, but despite his tendency to insult people, usually by accident and being unaware of normal social mores, will go out of his way to even help people that have in the past tried to kill, humiliate and/or rape him/her. If you want to know the result of getting Ranma actually angry, all you have to do is ask Saffron what made him re-incarnate most recently.
 * Heck, his opening move in that fight was to slice off Saffron's arm, whereas up to this point he was one of the few characters tended to go out of their way not to use maiming or lethal force. Do NOT endanger Akane.
 * Gohan in most of Dragon Ball Z is a pacifist who ahbors violence, but when provoked (namely by hurting his precious people, or just any Innocent Bystander for that matter), can fly into a near psychotic rage and suddenly increase his strength to colossal heights. Through this he was the first to unleash the devastating power of a Super Saiyan 2, which also turned him from the kind hearted boy he is into a brutally sadistic homicidal monster with the power to decimate entire Solar Systems!
 * Goku, even when fighting seriously to avenge fallen comrades or save the world, maintains a constant sunny disposition and childlike naivete throughout the series, allowing for humor in otherwise climactic battles. Goku only completely snaps when Freeza mercilessly kills his lifelong friend Kuririn. His first transformation into a Super Saiyan turns him into a cold, taunting, ruthless and arrogant fighter who starts to beat Freeza to within an inch of his life.
 * Future Trunks would fit this trope well. He's normally a quiet and polite guy, but one of the most merciless characters in battle. He won't even think twice about slicing his enemies and turning them into dust. Also, Vegeta learned not to underestimate Trunks' niceness when he taunted him and was blasted.
 * Al from Fullmetal Alchemist is a Gentle Giant who wouldn't hurt a fly, but he has come close to flying into a merciless rage (and actually does a few times in the first anime) on multiple occasions. You do not want to mess with those he cares about.
 * In the last episode of Death Note, The Ditz character Matsuda,.
 * In the last episode of Death Note, The Ditz character Matsuda,.

"Rushuna: You don't get a smile! *she proceeds to shoot EVERYONE*"
 * Nyuu from Elfen Lied is a cheerful, super cute blank slate girl, but try to hurt her and she will become Lucy, her deadly and stone-cold counterpart. Instant Head A Splode for you!
 * Lucy's first major massacre was a textbook example of a Beware the Nice Ones snap-out:.
 * Magic Knight Rayearth. Shidou Hikaru is a bubbly, animal-loving, always ready-to-help fourteen year old girl but don't hurt her precious Umi and Fuu or she might end up wiping the floor with you.
 * Naruto. The title character,  has a malevolent, nine-tailed demon fox of immeasurable power sealed into himself - and this fox's power has a habit of seeping out of him whenever he loses his temper.
 * Also, Nagato,  who was unusually kind and sensible as a child, but made a complete 180 after.
 * Chouji Akimichi and Hinata Hyuuga, two of the nicest characters besides the title one, also both quality for this trope. Hinata's timid, Chouji's placid, and both characters are extremely gentle and kind. However, harm the people they care about, whether by mocking and taunting them (Jirobo and Shikamaru, in Chouji's case) or, and they will get angry. Very angry.
 * The databook notes the stark change in Choji's personality by having two separate entries for him on the personality grid. Normal Choji is more toward the calmer and patient ends of the spectrum, whereas "Pissed" Choji is less so, and is one of the more passionate and less patient characters.
 * Sai is best described as this trope, he will sic his Drawings on you with a smile on his face and will cheerfully comment about the Short Comings of your member as if he were talking about the weather.
 * In Chapter 518, we see that Sai can be absolutely terrifying when you press his Berserk Button. He was relatively collected about the fact that  Sai then lost it and made short work of his opponents, his usual calm smile replaced by a Death Glare that would make even the most hardened shinobi cry for mama. Seriously.
 * Killer Bee is one of the nicest people in all of Naruto. The idea of holding a grudge is completely alien to him. He also beat Sasuke to within an inch of his life after the later initiated an unprovoked attack on the former.
 * After getting forced to play the sycophantic second fiddle to Akira Kogami for 19 episodes only to get sent out to hike up Mount Fuji for three weeks, lose his spot to a dumb Bishounen, and get yelled at by Akira because the water he brought back was warm, Minoru Shiraishi of Lucky Star's Show Within a Show finally lets Akira and her new assistant have it and trashes the set.
 * He's even drawn slightly differently after the event, changing from his permanent closed eyes to tiny, pissed off ones. Even when he's not pissed off.
 * Ayano, a Nice Girl with the tendency to be The Nondescript, also has one of the series' most angry Blue With Anger moments.
 * Komachi in Yes! Precure 5 is easily the most passive member of the cast, and her power is just a shield. Near the end of the series, someone manages to really piss her off. Turns out that shield can be used as an offensive weapon after all—and she carves out an interesting new feature in the landscape.
 * At the start of Neon Genesis Evangelion, Shinji Ikari is a loner and obviously has issues, but he's still generally quiet, kind and courteous. However, throughout the series, when the pressure on him proves to be too much, there's several occasions where he completely snaps and shows a violent, rage-filled side to his personality.
 * Let's not forget that this manic rage is mirrored in his Eva's attitude, as Shinji goes insane with bloodlust, so does Unit 01,.
 * Well,.
 * And then there's Rebuild of Evangelion. Oh dear sweet hell, Shinji is an unstoppable force of nature who is so nice, even smiling despite his heartache. And then you threaten Asuka or Rei and he will redefine Unstoppable Rage and Roaring Rampage of Revenge.
 * Holy Crap!
 * The dummy plugs are bloodthirsty berserkers, there's no doubt about that. However, they were based on Rei and Kaworu. Cue trope name.
 * Makoto Itou really had it coming.
 * Wolfgang Grimmer from Monster is possibly one of the nicest people you will ever meet... But do not upset him. Really, don't.
 * In Higurashi no Naku Koro ni, Rika herself notes, regarding the main cast, that, "They are all caring, gentle individuals. And yet,, they become controlled by delusion and start committing deadly acts of violence." Considering how much this anime seems to enjoy breaking cuties, this shouldn't come as a surprise.
 * In the end however, the Big Bad plotting all the terrible occurrences turns out to be an apparent Nice One as well,.
 * More so.
 * Quatre Raberba Winner, The Smart Guy of the Gundam Wing team, is sweet, sensitive, and polite, but once he loses  and the people in his colony turns against him, he builds a Super Prototype Humongous Mecha with two Big Fucking Wave Motion Guns and goes into a Tranquil Fury, destroying an entire space colony.
 * Building the Wing Zero was indeed the result of his going off the deep end and wanting to bring in an ultimate weapon to end the war. The resultant rampage (including the destruction of the colony), however, came about because he failed to realize why the design had been scrapped: the information overload of the cockpit caused a side effect of massive Mind Rape.
 * Gentle, selfless, fatherly Shuuichirou Oishi from the Prince of Tennis is pretty much the Team Mom of the Seigaku team. But press the very few buttons he has? Let's just say that pretty much no one can stop him in the two or three times he loses his patience on you. Well-shown when his beloved partner Eiji says something insensitive about him in public and Oishi screams and tosses Eiji to the ground.
 * And it's not only Oishi, either! Shuusuke Fuji also looks and acts cheerful, pleasant and polite, but if you do anything to piss him off (specially if you hurt/threaten his friends or his little brother Yuuta), you should pray he's not your next tennis opponent or isn't near to you for quite a while.
 * Outside of Seigaku, there's little Data Player Taichi Dan from Yamabuki. Sweet, feminine-looking, naive, etc - and is capable of yelling at Jin Akutsu, one of the most violent players in the whole circuit. Dan can be said to be Akutsu's Kid with the Leash, in a sense.
 * Not to mention Seiichi Yukimura of Rikkaidai. He looks feminine and kind, is very polite and soft-spoken, and strongly reminds you of the perfect Japanese woman... but he turns into a . Need I say more?
 * Code Geass's Princess Euphemia doesn't count, but shy little Fan Girl Nina Einstein certainly does. She's almost perfectly normal, aside from her deep-seated fear of Japanese people and her rather obvious crush on Princess Euphemia, who intervened to save her from Japanese terrorists.  , though, she promptly turns a previous offhand mention of her technical skill in a prior episode into.
 * A running gag among certain circles is that the sweetest, most innocent character, Nunnally Lamperouge, actually hides a horrible dark side that will surface if she ever gets a Geass of her own or indeed regains sight.
 * Considering what happens in the Nightmare of Nunnally Alternate Universe manga, the possibility is out there.
 * Suzaku definitely counts, though. He's an all-around Nice Guy who just wants peace, but will destroy pretty much anyone who threatens to upset the current peace. After the Euphemia example above, it just gets worse, since he outright stops being nice.
 * Suzaku a bit of a deconstruction because he was Hot-Blooded in his childhood to begin with. As pleasant as he can be in the present, his current drive for peace, though, is just part of a . Once the Euphemia example happens as mentioned, it's little surprise that his old bitter headstrong habits resurface.
 * Lelouch is a questionable one. He WAS a Nice Guy, but then his mother died, his sister was maimed, and his family abandoned him. By the time he walks through a village of shredded bodies, "nice" is just a mask he remembers how to wear.
 * He still does have a degree of kindness that roots itself in his desire to change the world, but there's no question that this series involves a great deal of his own catharsis. Even so, you can't deny he still did manage to show how much he was really holding back once he passes the Despair Event Horizon.
 * In Dangaioh, an ex Ordinary High School Student and Yamato Nadeshiko is the leader of the group that pilots the huge Super Robot that gives its name to the series. Why? Because Miya Alice is capable of unleashing ENORMOUS Psychic Powers once she's mad, frightened, or determined to fight and protect her partners: Roll, Pai and Lamda.
 * Rika from Kare Kano for most part is a quiet, unassuming girl but when she was a kindergartener, Rika found out that Kyo, an older boy who usually looks after her, was getting picked on, she saved Kyo from the high school bully by.
 * In Digimon Adventure 02, TK is normally a nice guy, unless you happen to be meddling in the powers of darkness, or trying (and failing) to whip him senseless, leading to a Falcon Punch in return.
 * and while Hikari doesn't tend to get angry, do not threaten/kill her friends, because that powers up her crest, enabling her to destroy you all.( or just power up agumon/ gatomon enough to kick some bad guy ass) case in point, Wizardmon and the Numamon
 * In Digimon Tamers, Takato is the least Hot-Blooded out of all the goggle boys of the series. Guilmon was this by default (naive, yet a powerful fighter, voiced by Masako Nozawa -- remind you of anyone on this page?), but Takato snaps when ...he was already not willing to forgive right before that moment, but what happens next is reminiscent of Adventure.
 * Chrono of Chrono Crusade is a Adorably Precocious Child that often gives speeches about The Power of Friendship and behaves politely even to people that don't trust him because he's a demon. But he is a demon, and when his powers are unsealed he turns into his true form—a bishounen powerhouse with massive amounts of power. When his Berserk Button is pushed, he's been known to fly into Unstoppable Rage fits with little thought to any collateral damage that may occur.
 * Don't mess with Simon the Digger. Seriously, don't.
 * Don't forget Nia! For the bulk of the series, she's just about the nicest, politest, most innocent character in the entire show. Until you find out she's actually
 * Played completely straight near the end of Inukami!. The local Yamato Nadeshiko (appropriately named Nadeshiko) finally snaps when the Big Bad of the series Nadeshiko prays to the Heavens for a power  and proceeds to wail on the Bigger Bad for some time.
 * Narutaru loves this trope, but the best example by far would have to be the local Lonely Rich Kid, Hiroko "Hiro-chan" Kaizuka. She's a quiet Ojou in sixth grade who is mercilessly bullied at school over her excellent grades, while at home her parents berate her whenever she gets anything less than a perfect score on any test (even though she's pressured by the bullies to do badly lest they torture her more). She tries enduring this abuse as best she can while remaining unconfrontational, but when the bullies take their actions to monstrous degrees and her father tries cutting off her ties with her only friend... well, let's just say she puts her new shadow dragon to very good use. The results are messy, to say the least.
 * Currently being toyed with in Detective Conan with Okiya Subaru, a friendly Sherlock Holmes-loving grad student living in Conan/Shinichi's house.
 * Conan's excuse for letting the fox-faced Subaru stay at his house: "A person who loves Sherlock Holmes couldn't possibly be evil!"
 * Don't forget Ran Morui, either. A beautiful girl with nice legs and a motherly disposition, okay? Well, either tell her you may have a shot at Shinichi's heart or threaten Kogoro, Conan, or anyone she cares for. Ran will show you no mercy.
 * Stepford Smiler Kafuka Fuura from Sayonara Zetsubo Sensei hides a bloodlust that makes those who are acutely aware of her cheerful facade mortally terrified of her. Her classmate Meru takes one look in Kafuka's eyes and is confident that one day, she will kill them all.
 * Hitohira. Beware of Nono when she's angry.
 * Negi-sensei is a prime example. Normally the ten year-old teacher is kindly to the point of adorable, but in more recent manga chapters he has been a particularly awesome example of this trope. At one point, he finds that  In addition, his recent acceptance of   makes him so fearsome that even his students are uneasy.
 * There's also an incident where Satsuki freaks out a couple of guys who try to start a fight in her restaurant.
 * Another incident where a group of girls are playing Keep-Away with Negi's ring/secondary wand in the bath. One of them grabs it and dashes across the water (it's a big bath) on magic shoes, leaping high into the air to get away. Tall, quiet Akira, who was helping Negi look for it, catches her in midair, hurls her into the water, then does the same to everyone else who was teasing him.
 * Chapter 265. HOLY SHIT.
 * Chapter 292 squares it with this.
 * Also, do not get Chisame pissed at you.
 * It has taken 280 chapters to get here, but we have finally found out what happens when you piss off Nodoka Miyazaki. Nobody actually gets hurt in the process, but the Big Bads' attack - until then verging on a Curb Stomp Battle - was stopped in its tracks, and is now presumably on its way to a complete reversal. Good thing, too.
 * Chachamaru is a nice, soft spoken robo-maid, who has a crush on Negi. She can also  by using the power of...cats
 * Even if you can survive the Kill Sat, do not hurt her. Negi does not approves.
 * Subaru from .hack//SIGN is about the most likeable character in the show. Then in comes the GIFT Affectionate Parody OVA where she poleaxes Ginkan for disregarding her orders so brutally that Censor Steam is employed in the scene (implying that it wouldn't be appropriate even for 17+ audiences).
 * Kurama of Yu Yu Hakusho is generally polite to everybody else and arguably the nicest member of the cast... unless you piss him off (threatening his mother is a good way to do that). Then he will kill your ass in very brutal and bloody way that involves lots of pretty flowers. Or worse.
 * Hiei noted this in an early arc, saying that Kurama's calm mind allows his be as calculating and brutal as he wants without being distracted. He even says that, back when he was a Psycho for Hire Big Bad, he brought Kurama along as a partner to avoid gaining his ire in the future.
 * And this is reinforced in the Black Chapter arc, where
 * Henrietta in Gunslinger Girl is as cute as a button... until an assault on her beloved handler Giuseppe brings back subconscious memories of her own childhood trauma. Then she proceeds to kill everyone in sight.
 * Actually, the organization that Henrietta is basically built on this trope, with a small battalion of cute, dormant psychopaths, including one who continually keeps a Limit Break saved up until she ends up being kidnapped in place of the bad guys actual target. Yea... that didn't go so well.
 * In Axis Powers Hetalia, Hungary, the cute young girl who was Austria's maid and later advisor before marrying him, will not hesitate to invoke her massive fighting skills (which she acquired when she was a pint-sized warrior girl) and maul you if you hurt her husband (Well, she might hesitate if you're a cute male and you're molesting him. And not always, mind you. You're warned, France)
 * And Lithuania? That nice guy? Quite a good spy and fighter who won't hesitate to put a knife to your neck if your threaten someone he cares for, specially his old friend Poland. You're warned, Prussia.
 * As a rule, everyone in the Baltic/Soviet region is a case of Beware the Nice Ones. Even the Shrinking Violet little brother of Lithuania, Latvia... Having a Psychopathic Manchild as your boss leaves marks on you, indeed.
 * As a child,  at one point completely kicked Turkey's ass. Turkey's 'I really hate kids' says it all. Greece is amused.
 * Let's not forget that, if you make the sweet Meganekko Canada lose his patience, you'll find yourself on the receiving end of a hilarious yet absolutely epic "The Reason You Suck" Speech. If America couldn't get his brother off his back for three hours straight, then so won't you.
 * Remember Finland? Finland? Sweden's "w'f"? Finland with the adorably off naming skills and the food preferences of a pregnant rat on acid? Well, while it's not shown in the strips just yet, plenty of fanfic has explored why it's probably best not to forget.
 * His partner Sweden is a Gentle Giant of few words who dotes on his "w'f", but in the aftermath of the April Fools' Day, it's him who thinks of the punishment for France.
 * Ukraine is a sweet Team Mom and Fragile Flower... who will subtly manipulate her younger siblings and will hold her ground if she has to.
 * Belgium is shown to be a rather Nice Girl prone to Heroic Self-Deprecation, but her profile refers to her as being scary when she's mad. The fact that she has a rifle and looks like she knows how to use it indicate that this probably would not be a good thing.
 * Mitsukuni "Honey" Haninozuka from Ouran High School Host Club is a short, blond cutie with a love of sweets and cute things, and is classified as the "lolishota type" member of the club. Renge cheerfully squeals about how he's so Moe. Harmless, right? WRONG! Honey just happens to be a black belt and heir to a family of VERY skilled martial artists. He's kicked the ass of grown soldiers twice his size, and strikes terror with a single look into the other hosts when they accidentally spill tea on his favorite stuffed rabbit.
 * That's his dark side, Dark Honey.
 * For a good idea of his kickass-ness, he was asked by Japan's Secretary of Defense to not fight in public, for if other countries saw him, they might accuse Japan of housing a WMA (Weapon of Mass Destruction)...
 * Don't forget Morinozuka "Mori" Takashi, Honey's cousin. He's usually very quiet, stoic, and passive... until he needs to kick ass. He's skilled in karate, and judo. Him and Honey make a formidable team.
 * Nadeshiko Fujisaki of Shugo Chara sweet, calm, polite, and all around pleasant...that is, unless, you happen to spark her character change. Note:
 * Shiho from Zettai Karen Children gets more and more aggressive tendencies as the series progresses—sometimes to sadistic levels. You really don't want her to use her telepathic abilities on you when she is in one of those moods.
 * Episode 40 confirms that this applies to Minamoto as well. Piss him off and you risk   or having him  .
 * Haruka Minami from Minami-ke is actually the scariest character in the entire franchise... in addition to being a Yamato Nadeshiko in development (and an Onee-Sama). She acts as a mother towards her two younger sisters. Remember how scared you got when you messed up & your mother lost her temper?
 * Hotaru Tomoe from Sailor Moon is a nice, peaceful girl...who can beat the demons just by looking funny at them.
 * Gundam Seed: Kira Yamato is generally a polite, soft-spoken person who cries easily, and as The Messiah, he's careful not to kill his enemies in combat, preferring to just disable their mobile suits, at least after he gets the Freedom. However, when the Big Bad needlessly kills his Fallen Princess ex-girlfriend Flay right in front of him (and right after they had just found each other, after much misfortune), Kira chucks his "No Killing" rule out the window, resulting in a spectacular fight sequence that culminates with him ramming a beam saber through the villain's cockpit and leaving him in front of his Kill Sat as it fires.
 * Another Gundam SEED example would be Miriallia Haw. As Gundam pilot Dearka Elsman finds out, Do Not make a snide remark to her when she's grieving and there is a sharp object nearby. You WILL regret it.
 * Mirajane. Read the chapters where someone nearly kills her "little" brother and you'll understand this trope like you never did before.
 * Fuyuki from Keroro Gunsou is normally an Extreme Doormat. Push him far enough, though, and everyone including Natsumi becomes scared of him. His expression is deliberately not shown during these times, but it's implied he looks a bit like a berserk EVA.
 * Tamama and Momoka, too.
 * Dororo is perfectly content to lounge around all day, drinking tea, and enjoying nature. But when the chips are down, he isn't afraid to demonstrate the skills that made him a top assassain back home.
 * Cho Hakkai in Saiyuki is polite and quiet-spoken and generally the nicest of the protagonists... unless he's pushed too far. When he really lets loose, he terrifies even makes-the-gods-nervous Goku. Sanzo has no qualms about taking on Goku or Gojyo in a tournament side chapter, but forfeits rather than face Hakkai without the use of his sutra.
 * For the most part, Major Alex-Louis Armstrong is the epitome of a Large Ham Gentle Giant. Emotionally scarred by the idea of killing civilians, always trying to give his opponents the chance of surrendering, had a terrible Heroic BSOD during the Massacre of Ishbal, etc... Then a homunculus goes and tries to kill his older sister. BAD idea.
 * Also, do NOT piss off Alphonse "Al" Elric. Seriously, DON'T. If his older brother Ed can't beat him in a fight, you won't.
 * Galaxy Fraulein Yuna's title character: sweet, bubbly, loves making friends with everyone she meets, whether they started out hostile or not. If you value your continued existence, absolutely do not kill any of her friends. Beating them up but letting them survive is apparently okay, but Genmu crossed the line and paid for it.
 * Tsubaki from Soul Eater is usually shy and humble. Thus, when she finally and truly stands up for herself in the fight against, the result was pure awesome.
 * Similarly, this series' personification of Death is not only a good guy, he's funny-looking and goofy -- The last guy who did that  *shudder*
 * Same goes for Demon Hammer Marie Mjolnir, a lovely, sweet lady who is also known as the 'Crushing Weapon' for a reason. When confronting the murderer of BJ,.
 * Spirit shows hints of this when he loses his temper with Medusa.
 * Patty's The Ditz, but she's a better fighter than she looks. She grew up on the streets, surviving by helping her older sister Liz mug random people. When she gets serious, she is much more horrifying than her Deadpan Snarker sister.
 * When it comes down to it, Yamamoto Takeshi from Katekyo Hitman Reborn definitely fits this. Put a baseball in his hands, or tell him to throw or hit something, expect him to get a serious samurai look and go absolutely all out on a simple game or task. Ask a poor, injured Lambo who just wanted to play catch. Though... This comes in handy sometimes. And don't forget Tsuna, at some moments. Especially when Genkishi decided to say he left Tsuna's friends for dead. Here comes the berserker rage. And recently . And Tsuna, who was planning to , doesn't do that, but willingly accepts it, with a pained look in his eyes as Yamamoto's attackers   Whether that new family has gone past Moral Event Horizon, to hurt Vongola, specifically, Yamamoto, Tsuna's still very... very upset. It's not normal for Tsuna to lash out, though, obviously.
 * Gon from Hunter X Hunter. Cute, lovable, Gon... don't hurt or threaten any of his True Companions. Seriously, don't. He's scarier than Killua when pissed.
 * Fruits Basket has at least two examples, if not more. Kagura Sohma is usually a cute, sweet girl with a cheerful disposition, but she actually shows her love for Kyo by beating him to a pulp on sight, especially if he refuses her advances. This frequently leads to Shigure's house being broken. When they were both little kids, apparently she got Kyo to propose to her by threatening him with a knife (or a big rock in the anime). Hatsuharu Sohma is usually kind, if eccentric and a little out of it, but when he snaps he turns into "Black Haru", a bloodthirsty version of himself with a whole lot of attitude. Both are not to be trifled with, and whatever you do, do NOT touch their love interests.
 * Andromeda Shun of Saint Seiya is a Technical Pacifist and is, on more than on occasion, called the kindest and gentlest of the five main Saints. He's the kind of guy who begs his enemies not to fight and lets them beat him within an inch of his life rather than fight a battle he doesn't believe in. That is, until you try to kill one of his friends. And lord help you if you're the bastard who murdered his teacher...
 * This trope is also the hallmark of the various incarnations of Hades, God of Death, mortal rival to Athena, and the instigator of the various Holy Wars throughout history. . Meanwhile, in the prequel series Saint Seiya: The Lost Canvas,  .  . His first act upon his transformation to Hades is to burn down their home town and massacre everyone in it.
 * In Yu-Gi-Oh! 5D's, Carly Nagisa is a sweet, eccentric girl whose love of The Lancer Jack Atlas is incredibly cute. However,  and unleashes a certified, factory-sealed can of whoop-ass on   This is done in a fashion that would be horrific if the bastard didn't completely deserve it.
 * Somehow,  but still. Dang.
 * Yami Yugi was never that patient with his opponents, but at least he tried to take a kinder route to defeating them, even if they threatened his friends. However, when he lost the soul of his partner, and local Jerkass Insector Haga tricked him into believing he had torn up the card that held it during their duel on a train during the DOMA arc...well, let's just say that it's a good thing that duels are supposed to end when a player's life points hit 0.
 * The episode after that one when Yami Yugi "meets" Yugi's lost soul in a kind of cursed land - and Yugi forces him into a duel, all the while snapping accusations at the pharaoh, and throwing Yami's earlier, cruel tactics right back at him. It was a being cruel to be kind-type situation, but the fact that Yugi could be that harsh at all was a shock to many fans.
 * Let's not forget the original Season Zero either, where Yami Yugi, in the first five episodes, sends all the bullies insane/in the Shadow Realm/dead/blown up(ok, that one was in a separate episode, but still...)
 * Yuuki Juudai from Yu-Gi-Oh! GX. Completely lovable guy who gets along with everyone, including people who have tried to kill him: right up until five of his best friends end up dead (or so he thought at the time). Cue Unstoppable Rage on Brron and the advent of Juudai's "if I have to be evil to stop evil, then I will be" philosophy.
 * And then he proceeds to conquer most of Dark World and suck up living souls to fuel Super Fusion with a loyal army of monsters at his beck and call. Brr.
 * Kamijou Maki from Hayate × Blade is perhaps the most notable example in her series. For almost 6 volumes, the readers hardly ever see her making an appearance for more than a couple of pages (which was even lampshaded in a side story), and when they do, she's portrayed as a whipped, mild-mannered, low-profile dork. Then one opponent breaks her right arm. Her response? "The judges can't stop me here. How lucky."
 * Miu in Kenichi: The Mightiest Disciple. Normally she's very amiable and rather pacific, but if you Miu mentions offhandedly that one of the reasons her grandfather traveled with her as a child was probably to get her immense rage under control.
 * Rurouni Kenshin as Battousai. The guy is a soft-spoken Martial Pacifist whom his girlfriend occasionally hits, and always tries to talk first and only attack later. But do not piss him off enough to have his Super-Powered Evil Side of sorts come out. We warned you.
 * Seras Victoria from Hellsing seems to start off as a sort of as a Wide-Eyed Idealist until the Valentines' attack on the Hellsing base sends her into an Unstoppable Rage which you might think hails from her vampiric nature, culminating in . However, a detailed look into Seras "Kitten" Victoria's history reveals she's had a vicious temper as far back as her childhood in an orphanage when she brutalized a fellow orphan who was bullying and tormenting her, and that she's been actively keeping that violent part of herself in check since long before becoming a vampire.
 * Misa Anehara from Yoku Wakaru Gendai Mahou is usually laid back and playful but is actually one of the most powerful modern-day magicians and deadly when serious.
 * From Pokémon: Ash's Pikachu. No, really.
 * There's also a Dragonite in one of the later Johto episodes that goes BATSH*T CRAZY after the Team Rocket trio grabs the Idiot Ball again and decides to steal a relic that it was guarding, resulting in the Dragonite destroying a significant portion of the garden it lived in while in an Unstoppable Rage. This turns into a Tear Jerker in the end, as after Dragonite snaps out of it and realizes what it's done, it breaks down crying. The worst part? Dragonite are normally FRIENDLY.
 * As of Best Wishes, Cilan. When he gets genuinely angry, he really gets angry.
 * It's not limited to heroes: James of the Team Rocket trio has typically been characterized as more pleasant and cheerful than his teammates, and a borderline Extreme Doormat to boot. He's only had two real flip-outs...one of which involved him trying to steal a skyscraper because his bottle cap collection had been stolen. The other had him attack Jessie and Meowth when they refused to team up with Ash, even though there were baby Pokemon--including James' Mime Jr.--in danger. Both of these happened before Team Rocket Took a Level in Badass.
 * In Pokémon Special, Yellow is everyone's friend. But if you threaten her forest in any way, you will be thoroughly stomped on by her usually-normal Pokémon roster...boosted to the mid level-80's on good old Viridian ragepower. Good luck, you'll need it!
 * Sasame from Prétear is one of the kindest members of the Leafe Knights. He's always supportive towards Himeno, tries to be the voice of reason among the older knights and resolves fights...
 * Trigun's Vash the Stampede is the sweetest, most gentle, peace-loving guy you could ever wish to meet, and manages to stay so despite all the horrible things that keep happening to him, and acts like a complete goofball most of the time when he's not angsting. He regularly manages to defuse dangerous situations and deal with opponents with minimal force, and sometimes without even having to fire his gun, despite the fact that if he really felt like it, he could easily unleash holy hell on everyone around him and pretty much nothing would be able to stop him. But if you do what Monev the Gale did, like blow up an entire city block and kill dozens of people in an attempt to kill him... well, the good news is, he won't kill you, but the bad news is, you're still utterly screwed. The scene when he looms up out of the darkness with an expression of pure rage on his face and his eyes glowing solid blue is chilling. He then goes on to completely thrash Monev using a vault door, the last three bullets in his revolver, a shot from the literal Hand Cannon in his cybernetic left arm, and a solid boot to the face, and reduce the huge, previously unstoppable assassin to a blubbering mess on the ground, begging for his life (and Vash was damn well considering putting a bullet between his eyes too).
 * Seto no Hanayome inverts this with Maki, who's introduced as a sweet, incredibly Moe character. Then as soon as she's alone with Nagasumi, she reveals herself to be a battlehardened (and psychotic) assassin on a mission to kill Nagasumi.
 * Played straight with San, who's usually a Yamato Nadeshiko, but will screw you up with her "Voice Shockwave" ability.
 * Elenore Baker from "Madlax". Go ahead and touch her mistress, Margaret...Just ask Maurice Lopez.
 * Rushuna of Grenadier. Sweet Ms. Fanservice whose goal is to get people to stop fighting by the power of her smile. When that doesn't work, she pulls out her six-shooter and blasts anything that moves. A castle full of riflemen led by an armored giant wielding a machine gun, who won't release the helpless prisoner?
 * Rushuna of Grenadier. Sweet Ms. Fanservice whose goal is to get people to stop fighting by the power of her smile. When that doesn't work, she pulls out her six-shooter and blasts anything that moves. A castle full of riflemen led by an armored giant wielding a machine gun, who won't release the helpless prisoner?


 * In So Ra No Wo To, Filicia is the soft-spoken, glasses-wearing Team Mom. Well, as long as you don't threaten or abuse any of her squad members, which'll make her remind you that she is after all a Lieutenant of the Helvetian Army and a survivor of the battle of Binnenland.
 * Nanami of Katanagatari gives us the impression of just being Shichika's sickly little sister. Then comes episode 4 and the Maniwa Insect Squad with the intent of capturing or killing her, and it turns into a one-sided slaughter. She even gives off a Slasher Smile while she's at it.
 * It's also worth mentioning that at this point of the story she seems to be . You should never underestimate nice characters...
 * A recurring theme in the Tenchi Muyo! universe. The main characters of the series set in this verse are all unassuming Nice Guys. Make them angry and they will end you.
 * Chiffon Fairchild of Freezing. One of the very few sane people among a student body of blood knights, she is still ranked number one in school...not to mention she has the Badass Nickname of the "Unmatched Smiling Monster". Uh...
 * Cardcaptor Sakura: Sakura is cheerful and caring, but the Snow card will forever remember what happens if she gets REALLY angry... During the fight Sakura loses the wristwatch Yukito gave her as a birthday present, and since she had a crush on him this triggers her Berserk Button. One-Hit Kill with the Fire card. Shaoran got really scared at that.
 * Keima's mother Mari, from The World God Only Knows, is a nice, simple Japanese housewife. Then Elsee pretends to be her husband's illegitimate daughter, and we find out she used to run with biker gangs...
 * In Durarara!!, the nicer you are, the more the character is messed up in the mind.
 * Stepping on Roses (Hadashi de Bara wo Fume) has several characters that start out as kind and caring, but through the series' events become deceitful, manipulative, or even all-out crazy... the most notable example of the latter being.
 * D.Gray-man: Allen Walker is a cheerful, kind young man who loves everyone, and has made it his mission to not only save humanity, but also release akuma-captured souls from their pain and suffering. But do NOT get him angry, because he will make the offender very, VERY sorry.
 * Yakitate!! Japan: Kirisaki Yuichi. Only in episode 1 though. The rest, he acts as Pantasia's Main Branch antagonist and wishes to crush the "cockroaches" (that is Azuma's gang of the southern branch).
 * Yoshitoki in Battle Royale, is normally shy and mild-mannered! When Kinpatsu Sakamochi/Yonemi Kamon depending on which media type you read kills  he goes beserk and runs at a armed man.
 * Kimba from Kimba the White Lion is a sweet and caring lion cub who is willing to help out those in need, a diplomatical and peaceful leader who tries to avoid fighting, and is more than happy to forgive those who want to reform themselves... But he also has super strength and vitality, the ability to summon many powerful creatures, which ranges from boulder-carrying hawks, and powerful chimps that fight along side him, and he puts all of that to good use in the battlefield; just look at all of the hunters, rhinos, hyenas, and other big cats he defeated.
 * Leo Aoi of Beast Master. Despite his scary face, he's as sweet as a guy can be, but when he sees blood, or God forbid, you try to hurt Yuiko, he will kill you if Yuiko doesn't stop him in time.
 * Mikael from Tenshi ni Narumon is usually an epitome of calmness, kindness and politness when dealing with strangers and people he's not close to, unless he's with Raphael -.
 * Mama is usually a kind and carefree house lady
 * Miruru looks like a cute, harmless cat-girl and acts like a total ditz most of the time
 * Muse is totally moe and looks like she's always on the verge of crying,
 * Sara
 * And also Ruka
 * Wako of Star Driver, the ever peppy south maiden, had never had a true moment of rage during the show. Then came episode 19. When glittering crux member Kou takes over Takuto's body, and tries kissing her. Something Takuto would never do. Did we mention it was her birthday? She puts Sugata's knife to her throat, complete with Death Glare, and drawing a little blood, and tells her, in no uncertain terms, it doesn't matter if she's controlling his body. She will cut her.
 * Of the two women central to the Leijiverse, Emeraldas is a merciless pirate and  Maetel is generally described as the Nice One: gentle, kind, a bit mysterious. The latter also blew up a planet because a mad doctor tried to steal her body.
 * No. 6:Sion. Just check out his reaction when Rikiga suggests Nezumi become a prostitute or when he . Nezumi even says Sion's not to be underestimated.
 * Rosario + Vampire has San Otonashi, a sweet, little girl (okay, not really that little) who doesn't speak and hates confrontations.
 * On the same note, after Tsukune gets his 'upgrades', it's generally not a good idea to bait him by attacking his friends.
 * And now he got those 'upgrades' under complete control, hoooo boy....
 * Toward the Terra has the Mu. They are a peaceful race of humans with Psychic Powers, who are hunted down like animals and chased across the galaxy due to Fantastic Racism and Deus Est Machina. Seeing, makes the survivors declare war on humankind and turns their leader into The Unfettered. They successfully conquer one world after another, leaving planetary defenses completely shattered, until humans finally mobilize all military forces and invent anti-Mu weaponry.
 * Dance in the Vampire Bund: Do not mess with
 * In R.O.D the TV it is eventually revealed that this happened with Yomiko and the Library. Joker kept pushing her and, when he finally revealed what he'd done to her lover... let's just say there's a reason you don't antagonist a Papermaster inside a library, especially THE Library.
 * The Hakuho Academy Space Yacht Club from Bodacious Space Pirates. Do not confuse them for a bunch of easily-scared high school girls if you value your retinas.
 * Koharu of Koharu no Hibi, definitely.
 * Gentle Giant Kurita in Eyeshield 21 is probably the nicest, most friendliest character in the entire series. He is also the main linesman of the Deimon Devilbats and he will crush you to protect his team. In fact, his strength increases the more people he has to protect.
 * Sena is generally a Nice Guy with being a bit of a coward. But insulting his teammates is one way to tick him off and you'll pay a heavy price.
 * Ooyuki from Urusei Yatsura is kind and gentle in the extreme. Once, Ran thought she had pissed Ooyuki off and was so scared she ran, throwing live bombs and grenades after Ooyuki just to buy time to escape. Ooyuki seemed completely unbothered and the friends made up. However, Ooyuki did give a stern (but softly spoken) lecture to the king lemming who had trashed Ran's place in the meantime, and the lemming ran off. Ooyuki said, "Oh? Do you think you can run away?" The resulting punishment and collateral damage thereof caused no small amount of mental trauma to the lemming and any witnesses.