When most people think of The Quiet One, they may also think Extreme Doormat or Butt-Monkey alongside it. Whether they are one or not (half the time they are only seen that way), subject them to one round too many of Break the Cutie and the like, and, if it isn't preceded by a Death Glare, they will give you a 'not so quiet' moment.
Maybe Bob pushed a certain button, maybe those anger management classes Alice used to take are starting to wear off, maybe Alice has been angry all this time, it just never showed or no one took it seriously. Maybe this is her first time dealing with anger.
This rage is almost always expressed verbally, though violence can also be included. Their verbal attack can differ from an ego-brusing "The Reason You Suck" Speech, a mentally scarring Breaking Speech or an emotional "World of Cardboard" Speech. If they are also The Stoic, they might also ask the offender "Did You Think I Can't Feel?" before ranting about all they have been put through. One might also catch a swear or two.
Another version could be when the heroes' team is in low spirits, and The Quiet One, fed up with all the sulking, throws the table (or something else) to the side and gives a Rousing Speech to their comrades.
Usually a Moment of Awesome when they are shown to finally speak up for themselves, but can change depending on the character or the setting. For instance, Take This Job and Shove It can easily cross the line into Going Postal if the quiet one completely loses it.
The main difference between Beware The Quiet Ones and its sister trope Beware the Nice Ones is while the latter is known for their kindness, the former is known for their (near) silence, though they can overlap sometimes. See also Beware the Silly Ones if they're a bit... well... strange.
- Durarara!!: Mikado Ryugamine is a great example of this trope. He may seem quiet and nice, but underneath he's quite unstable due to being a closet adrenaline junkie. He's the leader of the Dollars, for another. You do not want to tick him off.
- Near-Invisible Canada from Axis Powers Hetalia is a good example: Butt-Monkey? Check. Shrinking Violet? Yep! Giving America "The Reason You Suck" Speech? A true Moment of Awesome.
- Machinedramon from Digimon Adventure is a villainous version. Don't let his whispered monotone fool you; he's as powerful and sadistic as any of the other Dark Masters.
- Lupin the Third's colleague Goemon Ishikawa XIII barely says a word...preferfing meditation instead of jabber. Upset him or threaten his friends and he'll use his sword to slice your clothing off...or worse...before you can blink!!
- Tetsuya Kuroko from Kuroko no Basuke is a good example as well. Practically invisible, he doesn't really talk much and people don't notice him. But if you try to dirty the game of basketball through nasty tricks...
- Bertolt Hoover from Attack on Titan is a soft-spoken Extreme Doormat with absolutely dismal self-confidence. He spends much of his time lingering around the others awkwardly, and rarely offers more than a few words. He's also a highly skilled soldier, graduating 3rd in his class, and fiercely protective of the people he cares about. He also happens to be the Secret Identity of the Colossal Titan, and as such a Person of Mass Destruction responsible for wiping out 20% of the human race. While remorseful over it, he's fully prepared to do whatever is necessary to accomplish his mission. Beware the quiet ones, indeed.
- Ai Enma, the titular Hell Girl is the most reserved character in the series as her job requires her to suppress her emotions to the point where it is very difficult to make her angry... God help you if you actually succeed.
- Shiryu from Saint Seiya is a softspoken Genius Bruiser with lots of common sense and a great devotion to his Master, his Childhood Friend, his Goddess of liege and his True Companions. He also represents the Dragon constellation and wears the Dragon Cloth... and according to Shiryu himself, the Dragon is calm and wise until those he cares for are threatened/hurt/killed/etc. in any way. Guess what happens to Shiryu whenever this happens? And even more so if either his Master or Childhood Friend are the one in danger...
- Rinne from ViVid Strike! was a Shrinking Violet who tended to avoid attention and became the primary target for a trio of bullies at school. She tries to endure it for a few months, until they knocked her out when her grandfather was dying, keeping her from seeing him one last time. The next day she gave them a brutal yet well deserved No-Holds-Barred Beatdown.
- Sailor Moon examples:
- Hotaru Tomoe/Sailor Saturn is the calmest and quietest out of shyness. She also has the ability to annihilate any life form on Earth and neighbouring planets by dropping her scythe, and in the manga has verbally destroyed two girls who were trying to take her spot as Chibiusa's best friend.
- Michiru Kaioh/Sailor Neptune is usually the calmest and quietest after Hotaru. The few times she loses her cool, however, she becomes absolutely murderous, and in one occasion she had to be kept from killing Yaten for hitting a previously unknown Berserk Button of hers-namely criticizing her choice of lipstick and stealing her spot as the school's make-up expert. Fittingly, she's Hotaru's adopted mother.
- Shigeo Kageyama is a quiet, timid and physically underwhelming middle-schooler. But he has incredible Psychic Powers even though he does not want to fight. But when his emotions saturate, his power increase immensely and the emotion he is currently feeling flows out (and if you made him angry, good luck).
- And sometime, if he loses consciousness, ???% comes out. This Superpowered Evil Side (the subconscious manifestation of Mob's full potential) can extract the energy around him (even his enemy's psychic energy) and possesses insanely powerful psychic powers (though it mostly comes out to protect mob).
- Hinata in Naruto, overlapping with Beware the Nice Ones. She's one of the quietest characters of the series, mostly out of shyness, but when push comes to shove, she can push back, especially when it comes to defend her loved ones.
- Ao Manaka in Asteroid in Love is often defined by how quiet she is, since she has a reluctance to speak due to past trauma. The one time when Mikage indicates she won't mind if Ao's Childhood Friend Mira got interested to geology and switches to the her side of the Japanese School ClubBackground , however, Ao responds with such anger that her Girlish Pigtails flies horizontally, and gives Mikage such big Death Glare that sends Mikage crying Tears of Fear.
- Fans of Blink may not know that she was introduced on Earth-616 during the Phalanx Covenant as a very shy, introverted girl named Clarice Ferguson who was terrified of her own powers. When she finally cut loose, she killed the formerly unstoppable Phalanx unit that had been holding her and a group of other young mutants captive... at the cost of her own life. The Blink who joined the Exiles was from an alternate timeline.
- Monet St. Croix was introduced in the same storyline, and also fit the trope. She spent most of her first issue silently studying Phalanx technology until she could identify the impostor hiding among her fellow mutant prisoners. Then she hit him with a Megaton Punch and led a breakout. Even cooler than it sounds — she appeared to be catatonic at first. Turns out this was just a super-intense state of concentration, and she'd worked everything out... look out, Phalanx.
- Batgirl (2000): Cassandra Cain was originally mute, and after learning speech she doesn't talk much. That's because her dad taught her to talk with her fists. Heaven help you if you get her mad.
- Spider-Man: The Spot used to be a Spider-Man villain known for being largely ineffectual and mouthing off. Then he got trapped in the dimension he teleports through. Now he's mute, insane... and probably one of the deadliest killers alive.
- Spider-Man himself usually cracks jokes and makes insults while fighting bad guys. But when Spidey stops talking, it's a sign that he's really, really pissed off... and that whoever's responsible is in for a really bad time.
- The Inhumans: Black Bolt. Whenever he utters a sound, it destroys things on a major scale. That is to say, a whisper from him is on the level of a nuke.
- X-23 rarely spoke at all in her first appearance (NYX) and origin story, (Innocence Lost) and even after is a laconic girl who generally shuns the company of others. She's also a highly-trained assassin and one of the most dangerous killers in the main Marvel Universe. God help you if you harm one of the handfuls of people she actually cares about.
- Axis Powers Hetalia fanfic Gankona, Unnachgiebig, Unità: Japan is The Quiet One in spades. Anger him enough, and he will show his true power. Just ask Germany. Despite being a full six inches taller and being a lot more muscular, their fight was nowhere close to a Curb-Stomp Battle.
- A Crown of Stars: Rei was always quiet, unemotional and physically unimposing. Then she got pissed off with Asuka after a Cat Fight and destroyed a dimensional portal to prevent Shinji and Asuka from leaving their homeworld... a dimensional portal built by a god!
- Advice and Trust: Rei is a calm, collected, soft-spoken person. During the entire battle against Zeruel she acted in a determined but non-aggressive fashion. Then the Robeast tried to strike Shinji and Asuka. She went full-on berserker on its posterior, completed with glowing red eyes and furious snarls and growls.
- The Child of Love: Rei is usually tranquil, quiet and passive. Then Gendo threatened her niece, Shinji's daughter. Explosions and violence followed.
- Doing It Right This Time: Rei was calm, reserved and little communicative. Then she got sent to the past, and she was feeling suitably angry. She slapped Gendo to pay him back for mistreating Shinji and several months later tore an Eldritch Abomination apart to vent her anger.
- HERZ: Rei is usually quiet, calm and non-confrontational. Then a pack of loonies tried to shoot her niece. The cleaning crew had to scrub their remains off the walls.
- The One I Love Is: Rei was a quiet, calm Emotionless Girl seldom spoke and obeyed her Commander's orders without question or hesitation. But if something or someone threatened Shinji or her relationship with him, she became hostile and even violent... especially to Asuka since Shinji was falling for her. Her relationship with Asuka became very strained and belligerent until they got a very bitter argument and a pretty virulent Cat Fight. Although that fight ended in a stalemate Asuka noted Rei was very quiet but she could be quite savage and hit hard if provoked.
- Rosario Vampire: Brightest Darkness: Dark Kuyumaya is very much The Stoic, rarely expressing emotion or even talking much. This hasn't stopped him from hospitalizing several bullies at Yokai Academy or going One-Man Army on a Fairy Tale squadron.
- Some Semblance of Meaning: Vale is usually The Quiet One and Shrinking Violet but don't piss her off.
- Brandon in Betray Me Not talks very little and only speaks up when it's really necessary like in the anime, but once his Berserk Button is pushed too hard, he'll turn into a Screaming Warrior, and if there's a gun nearby, he'll unload everything at you.
- Rei in The Second Try isn't a violent person. She's pretty much emotionless, very quiet and talks little. However, threaten her niece and shell make you wish youre dead.
- The Sanctuary Telepath: Janine doesn't speak much but don't let that fool you - by the time you'd start put your plan in motion she's already seen everything about it in your mind and taken the necessary steps. Perks of being a telepath and all.
- Her Inner Demons analyzes Sci-Twilight's One-Winged Angel transformation during climax of My Little Pony: Equestria Girls Friendship Games as this. Sci-Twi grew increasingly vindictive toward her classmates, to the point where she sought power to fight back, enough to become Midnight Sparkle.
- As the title suggests, Always the Quiet Ones involves Sunset and the other Rainbooms becoming convinced that Fluttershy is really a psychotic killer.
- Becoming Lífþrasir: Dogsbreath has rarely seen Hiccup angry, so he was rather impressed that Mildew was able to do it in less than a minute.
- Snotlout thought it would be funny to make Ruffnut slip on ice while she was three months pregnant. Fishlegs then proceeded to have Snotlout strung up by his ankles naked. He refused to let him down until Stoick made him.
- Tales of the Undiscovered Swords: Kiriha Sadamune quietly endures the bullying his Big Brother Bully Ishida dishes out at him for a reason he had no control over until the latter shows his full Yandere colors and decides to murder the saniwa, which is when Kiriha kicks some serious ass and stops the murder attempt in one of the most graphic violence scenes in the series.
- In Amazing Fantasy, Boomerang is a meek Extreme Doormat who rarely speaks his mind but possesses unhealthy amounts of Undying Loyalty to the Enforcers. According to Vulture, a slight against Clash sent Boomerang into a berserk rage in which he brutally murdered the offender.
- In fernwithys ''The Golden Mean]] we get a glimpse of this with O.C. Stand-in Paulin Gibbs (man to be the male morphling), in the sentences before his death, when he attacks Enobaria bare-handed and actually knocks her down before getting it In the Back from a nearby Gloss.
Haymitch: His usual vacant expression is gone, and for the first time since his games, I see the boy who won. He wasn't a clever player, but when he was raised to anger, he was terrifying.
- Matsu, the main character of Joshuu Sasori, has a knack for patiently and silently enduring whatever mistreatment gets thrown her way and waiting for just the right moment to unleash violent revenge on those that wronged her. This is why she is called Sasori, or "Scorpion."
- Dead Poets Society: The shy and insecure Todd Anderson spends most of the film struggling to get out two full sentences and is overlooked by the school and his parents. After his best friend kills himself, the school tries to bully him (and the other boys) into pinning the blame on their favourite teacher - and he leads half the class in an outright rebellion against the headmaster.
- Gaear Grimsrud from Fargo. He hardly ever says a thing throughout the entire movie (something lampshaded early on by Steve Buscemi) but if provoked or put in a situation where he might get caught... well, let's just say that you don't want to be near him and a gun. Or an axe for that matter... or a woodchipper.
- Don Vito Corleone from The Godfather is famously very soft-spoken, even hoarse, but an extremely menacing screen presence.
- Star Trek Into Darkness: After Kirk died, Spock proceeds to beat the ever living crap out of John Harrison/Khan.
- In Ghostbusters (1984), Walter Peck shuts down the power to the Firehouse despite Egon's dire warnings that it would be like dropping a bomb on the city. This results in an enormous explosion and hundreds (possibly thousands) of ghosts being released back into New York all at once. Peck orders some nearby police to arrest the Ghostbusters, claiming they were directly responsible for causing the explosion. Egon completely loses it, screams "YOUR MOTHER!!" and has to be physically restrained from tearing Peck apart with his bare hands. Remember, this is Egon Spengler!
- Office Space: Beware Milton. Or he'll set the building on fire.
- Thor's antagonist, Loki, started as the often pushed-aside, quiet, intelligent younger brother who was given too much power at exactly the wrong time.
- The Drop has Bob, who though meek rarely gets rattled. And when he's given reason to fear for those he loves? Watch out.
- Vice: This is the central theme, as introduced by the epigraph stating that quiet men plot and bide their time while others act and then strike when it is most opportune. Dick Cheney himself is presented as the quintessential example of this type of man.
- TRON: Alan T. Bradley. Meek and harmless looking computer geek. Completely scrupulous. Won't even do his banking on company time. Establishing Character Moment? Laying out in a perfectly calm and friendly manner that the software he worked on for months (the title character) is going to completely screw two of the antagonists as soon as he compiles the last upgrade and hits "run." He also seems meek, hamless and fatherly come the filmed sequel, but the first shot of him on-screen is showing him about defend young Sam from nosy reporters with physical force if necessary. Oh, and the "Flynn Lives" thing? He's been running the whole thing under everyone's nose. In the alternate sequel of TRON 2.0, he figures out how to crash a server from the inside just by analyzing the schematics. His son has to do the actual fighting, but Awesome by Analysis? You bet.
- Dark Life has Pretty. Despite his name, he is not someone you want to annoy.
- Theodore Sturgeon's short SF story "Extrapolation" was originally published under the title "Beware the Fury", as in the phrase "Beware the fury of a patient man". Wolf Reger is a brilliant but aloof and antisocial scientist/astronaut and humanity's future depends on his actions. When he is captured by alien invaders , Earth's governments all think he has turned traitor. But he manages to destroy the alien fleet single-handled without even using a weapon.
- Harry Potter: Quirinus Quirrell is the nervous, mostly unnoticed and seemingly innocent character throughout the entire novel. However, at the end it turns out that he has been possessed by Voldemort all along and has been trying to kill Harry all through the book. However, he was probably being controlled by Voldemort by this time as he had been taken over after trying to seek him out to destroy him in his weakened state, trying to earn some respect from his friends and fellow school pupils that had laughed at him for so long.
- And then there's Peter Pettigrew.
- Harry himself is actually rather quiet and introverted. He's also rated as the best fighter in his class, and he won't hesitate to battle anyone who messes with his friends.
- Sarah 'Scout' Mason of Heretical Edge is a rather tragic example. Her mother disappeared in a monster attack when she was seven and she's barely spoken since. She's also an extremely skilled Friendly Sniper with a gun that creates portals: she does things like create fences of looping bullets to deal with super fast enemies.
- Ben from The Leonard Regime is much more reserved than most of the other characters, bur provoking him is never a good idea.
- In The Outsiders, Johnny was the most quiet and most law-abiding of the greasers but when he sees his friend Ponyboy being drowned, he stabbed and killed the attacker.
- A Practical Guide To Evil has Eudokia, The Scribe. She's usually found in the corner with a lapdesk, quietly catching up on correspondence or whatever. She's also essentially the entire spy network for The Empire, and when it comes to not seeing her coming, she's said to be as dangerous as Assassin. A few words in the right ears at the right time, the correct paperwork filled out and verified [redacted] was, officially, never even a little problem to have managed existing.
Captain Jarad, the Webweaver said, ignoring the Dunis spluttering as her eyes sought out the Soninke whod been about to be chewed out by her earlier. Congratulations, you are now a commander of the Ater city guard.
The young man saluted, hands shaking.
What is to happen to Com- former Commander Barsina? he asked.
Scribe met his eyes.
I know of no such individual.
A heartbeat later, an enterprising guard behind the former commander slipped a knife in the Dunis back.
- Steapa from Bernard Cornwell's The Saxon Stories. Quiet and originally believed by the protagonist to be a half-wit, he becomes an absolute killing machine in battle.
- And, in a more specific example, there was Steapa's complicated test of loyalty in the second book. Steapa's sworn lord, Odda the Younger, had ordered him to kill Uhtred (who had brought Odda orders from King Alfred to attack the Danes). Steapa accepts the orders without comment, stands up to face Uhtred silent and grim, then turns and kills Odda.
- Roose Bolton from A Song of Ice and Fire is one of the most powerful lords in The North, and bannerman to the Starks of Winterfell (the "good guys" of the series). His obsessive habit of leeching himself leaves his voice very weak and whispery, so that everyone has to lean in to hear him speak during strategy conferences, and he loses the first battle he's sent to command in. Later, he betrays and personally murders his liege, King Robb, and is declared the new Lord Paramount of the North. It turns out he was working for Tywin Lannister all along, and kept over half of Robb's troops sitting on their asses for the war, later sending most of them to die in a pointless fight. Even the Lannisters underestimate him, as it turns out that after Tywin Lannister's death and the complete anarchy that falls upon the kingdoms, Bolton may be considering declaring himself the new King in the North and seceding, since the southeners wouldn't be able to do much about it anymore. Of course, the House Symbol should have been a hint.
- Tortall Universe: Beka Cooper. While she's paralyzingly shy, she's very good at chasing down criminals and fighting. (She does become less shy, but rarely chatty.) She has also been known to blow up at people who have been frustrating her over a long period of time.
- Mistborn: The Original Trilogy: Vin is a shy, quiet girl who rarely wastes words. By the end of Book 1, she's also probably the most dangerous Allomancer alive, and will stop at almost nothing to protect Elend and her loved ones.
- The Raven Tower: The Strength and Patience of the Hill is a quiet god who, thanks to Time Dissonance, often mulls over thoughts for years or generations and who rarely acts overtly. Then an enemy tribe with divine assistance attacks its people's village and kills its favourite priestess, and it immediately strikes the god dead.
- Firefly: Simon. Messing around with his sis is not a smart idea.
- Buffy the Vampire Slayer: Willow and Giles.
- Person of Interest: Reese tends to whisper when he talks. He prefers to let his actions speak for him.
- Then there's Finch, who prefers to let his computer skills and Arbitrarily Large Bank Account do the heavy lifting for him - but in those instances where everything is on the line, he does prove capable enough to, say, escape an interrogation room guarded by the FBI and Samaritan's agents with no real-life backup.
- Breaking Bad: the Cousins, a pair of assassins working for the Cartel, barely say a word in all the time they appear in the series.
- Ronnie Gardocki was by far the least noticeable or interesting member of The Shield's Strike Team originally, but by the final seasons it was shown that his quiet demeanor hid a ruthless, ice-cold professional.
- Star Trek: The Original Series: Spock definitely. He may be The Stoic but don't screw with his captain or the ship.
- Merlin: Guinevere. Don't tick her off, don't mess with her friend, or betray her knights, or you'll get executed.
- Star Trek: Enterprise: Malcolm is easily one of the most introverted and least talkative people on the ship. He's also the guy who's officially in charge of blowing stuff up, which he's only too happy to do, so don't threaten his crew or his captain.
- Sherlock: If you don't want to get slapped by Molly, don't do drugs. Sherlock can attest to that. Really, he can. John witnessed this. And called him out on his idiocy for it. Understandable, he was an idiot for doing that.
- Sherlock might be The Stoic, and John might be very reserved, but don't mess around with them.
- Sherlock told Moriarty in no uncertain terms that if he harms any of his friends, he's pretty much screwed.
- And killed Magnussen in front of everyone.
- We all know John killed two villains and threatened death on one of them.
- "Let him go, or I will kill you."
- Also, Molly stood up for herself in "A Scandal in Belgravia".
- * The title character in William of Orange has a nickname: William the Silent. He was called this for guarding his opinions and ever being pleasant to those around him. He later becomes the leader of the Dutch revolt against the Spanish king.
- The Adventure Zone: Balance: Lucretia is usually the only one of the Red Robes not to speak, usually lampshaded by Merle. Despite this, she runs the Bureau of Balance, survived Cycle 65 on her own during The Stolen Century and was the one to feed the memories of The Stolen Century to Fisher.
- Dane Cook had a comedy bit where he talked about heist movies invariably having that one guy on the team who is a combination of this and Psycho Party Member.
There's always that one guy on the team too, he was a last minute replacement. He's not one of the original gang. But one of the other guys vouches for him. 'No, no, dude... trust me, this guy's cool. He's solid and he's cool.' But he's not cool, is he? He doesn't really say anything ever, right? He just stands there, looks cool... and then at one point he might be like... 'Let's kill these bitches.'
- George Carlin didn't think much of this trope.
"It's the quiet ones you've got to watch." You know that one, eh? Every time you see a story about a Serial Killer on TV, what do they do? They bring on the neighbor. And the neighbor says, "Well, he was always very quiet." And someone in the room says, "It's the quiet ones you've got to watch." This sounds to me like a very dangerous assumption. I'll bet you anything that while you're watching a quiet one, a noisy one will fucking kill you! Suppose you're in a bar and one guy's sitting over the side, reading a book, not bothering anybody, and another guy is standing on the front with a machete, banging on the bar, screaming, "I'll kill the next motherfucker who comes in here!" Who are you going to watch? You're goddamn right.
- Warhammer 40,000:
- The Necrons are an entire army who used to lack the ability to speak wholesale (and mostly they still do), but even their most basic Gauss guns shoot what is essentially green lightning and can automatically wound on a dice roll of 6. They are also essentially Space Terminators — they just keep getting back up after you think they're dead, putting themselves back together and continuing to march on your position until you or they are utterly annihilated.
- The Sisters of Silence, a little-seen Amazon Brigade army of the Imperium whose initiates take a vow of silence on entering the order and communicate through sign language from then on. They are still the Imperium's dedicated anti-psyker specialists, and are able to destroy Daemons with their grenades.
- Westeros: An American Musical: Roose Bolton gets introduced as a member of the Northern army alongside Greatjon Umber, who's the most vocal of the two about having to follow the command of the teenage Robb. After Robb puts Greatjon in his place, Roose becomes just an extra member of Robb's background ensemble until a scene in which Robb gives him command of part of his army. The second song in which Roose is seen ends with him killing Robb with his own hands, an act that indicates his quietness has been hiding a much more dangerous personality all along.
- Edgar Ross of the Red Dead Redemption series. He barely speaks in his few appearances in II, but once Andrew Milton kicks the bucket, Ross descends on the Van der Linde gang with an army of Pinkertons, yelling threats through a megaphone. At this point, he's clearly fed up and just wants the gang dead. And while he's more talkative in I, the beware part is still very much present.
- Saito Hajime in Hakuouki is the quietest member of the Shinsengumi and the one who can always be depended on to follow orders scrupulously and faithfully. He's also the most lethal swordsman of the group and practices iaijutsu specifically because it allows him to end most of his fights before his opponents know they've started.
- Played for Laughs with Mio from Little Busters!. On the surface she seems like a delicate, fragile Emotionless Girl. And indeed, her physical stats are quite low. But she's very intelligent and downright ruthless at times, such as when she takes advantage of every slight lapse in attention on Haruka's part during the newspaper fight and is able to hit her countless times, or when she performs an absolutely devastating take-down of Haruka's joke when they're only supposed to be performing a simple Boke and Tsukkomi Routine.
- Kiryuu Moeka in Steins;Gate is a very socially withdrawn woman and prefers to let her text messages communicate for her instead of talking. Even when the person she's texting is literally standing right in front of her. Take a guess at what happens when you steal her phone.
- My Harem Heaven is Yandere Hell has Kanna who is a reserved stoic. Oh, and she's one of three selectable yanderes.
- Grisaia no Kajitsu: Sakaki Yumiko may be the least social of the Mihama students, usually keeping to her books or locking herself up in her room, however she is also the last person you want to piss off. That could easily result in an outburst of violence, making her draw her signature boxcutter and brandish it menacingly.
- Katawa Shoujo has Hanako's Bad Ending. After telling Hisao to Get Out! of her room repeatedly, she explodes at him (and the player) for pitying her and treating her like The Woobie all throughout her route. It comes off as a major Player Punch.
- Finland from Scandinavia and the World has this moment, where he shouts Perkele 306 times after losing to Denmark in hockey. Actually, he fits the trope pretty well in general, given that he's a chronically angry Knife Nut who rarely speaks.
- Yuki Sonada kind of fits this trope (more since her magical girl abilities awakened, than in her earlier appearances). That is, assuming she's not just being stereotyped as an over-emotional teenage girl.
- So do Piro and Ping, but if pushed over the edge they can be physically violent, too.
- In El Goonish Shive, Charlotte is introverted and socially retiring, yet manages to tackle a spider-vampire about to launch a surprise attack on Diane. The creature easily tosses her away, but still.
- On Strip Search, Katie Rice is absolutely the quietest person in the house, but it soon becomes clear that she's also one of the best competitors — starting when she wins two elimination challenges in a row.
- The Noob franchise has Ivy, narcoleptic and apparently not much more aware of what is going on when awake. But just try attacking one of her guildmates while turning your back to her...
- DSBT InsaniT: Asia doesn't say much and is very polite, but she will stab you with thorns if you push her too far.
- This story from the subreddit, ProRevenge, is this trope in a nutshell.
- Goof Troop: PJ has occasionally gotten angry at his friend and dad, but other than that, he's quiet.
- Raven from Teen Titans may be reserved, but god help you if you really piss her off by messing with her friends. It doesn't help that she's half-demon, and destined to cause The End of the World as We Know It.
- Flora from Winx Club is sometimes thought to be a pushover because of her shy nature, hesitance to harm living things, and the nature of her powers. But time and again, she proves that nature is not so harmless, especially in Tears from the Black Willow, when the Trix hit her Berserk Button. And who wants to bet that it's messing around with her friends?
- My Little Pony: Friendship Is Magic:
- Fluttershy is the quietest member of the mane cast, on account of being, well, shy. Then comes "The Best Night Ever". When she's avoided by the forest creatures of Canterlot... well, see for yourself. Fluttershy in "Putting Your Hoof Down." Dear Celestia.... She displayed this way earlier, in "Dragonshy" and again in "Stare Master". "Dragonshy" is the episode where the fans learned that you do not mess with Fluttershy. From Season Four, "Power Ponies" demonstrates that you wouldn't like Fluttershy when she's angry.
- Don't mess with her friends. Seriously, don't.
- Also, Celestia help you if Big Macintosh raises his voice.
- The Transformers: Prime version of Soundwave speaks using others' recorded sentences (when he speaks at all), rarely ever has a major starring role... and can bash in heads with the greatest of ease, as Airachnid can attest to. He's the second-most feared Decepticon on the Nemesis, right under Megatron himself, and with good reason. Knock Out even says "Watch out for the quiet ones" to Breakdown after Soundwave curbstomped Airachnid. Wheeljack fared slightly better against Soundwave than Airachnid did. But only slightly. To put this in more perspective, Wheeljack had an easier time against Dreadwing. Soundwave is eerily silent when he fights, too. It's kinda Creepy Awesome.
- In Transformers Animated, Prowl definitely qualifies for this. He's a sleek, dark ninja who doesn't really like anyone else, prefers to sit in his tree and meditate.. but when he fights, he wins, most of the time.
- Kenny from South Park, normally both The Quiet One and The Unintelligible, certainly qualifies as of the "Mysterion" story arc. He says the most he ever does during these few episodes, and his Berserk Button is revealed; do NOT mess with his little sister.
- Arthur: Fern is very quiet, but she will go all out with revenge. She managed to make Francine cry (in "Draw!"), and tricked Brain into thinking giant worms were attacking Elwood city (in "War of the Worms").
- Steven Universe features Lapis Lazuli. Barely taller than Steven, she's rather withdrawn and quiet- and also a hydrokinetic Person of Mass Destruction who can lift the entire ocean at once. Her first appearance has her calmly introducing herself to Steven- and a moment later, one-shotting Garnet with a huge hand formed out of water. Later episodes have her fusing with Jasper to drag their combined form underwater in a scene that calls to mind Dragged Off to Hell.
- Garnet herself is the more reticent and (relatively) level-headed of the Crystal Gems, and very capable of taking charge when needed.
- Ice Bear from We Bare Bears is the most reserved out of the three bear brothers, but he is also The Ace of the trio and wields an axe. The "Icy Nights" episodes turn Ice Bear into a bona-fide action movie hero, showing just how dangerous he can be when he or the ones he loves are threatened.
- Hey Arnold!: One of the kids, Curly, had been waiting to be the next ball monitor, but his teacher Mr. Simmons accidentally skipped him. Curly didn't take it too well. After everything blows over Helga remarks that the quiet ones should never be trusted. Curly also framed Eugene for pulling a false alarm because he'd ruined his favorite pencil.
- The Simpsons has Maggie Simpson. On the surface, she's a voiceless baby who is the youngest child and (in comparison to everyone else on the show, especially her own family) has had little to no Character Development, but has shown to be very loyal to her family and has saved them (namely Homer) on several occasions, is much more wily than she lets on and even knows how to fire a gun.
- Droopy falls under this in several of his animated shorts. Repeatedly humiliated by his adversary, he never reacts...until it looks like he's about to lose "The Dame". Then he responds, in the same monotone as always, "You know what? That makes me mad," and can suddenly fling his enemy across the room with ease.
- Looney Tunes: The Minah Bird from the Inki cartoons. He's always just walking (and hopping) around quietly, but whenever somebody tries to hunt/chase him, things will go bad for them. Heck, in his appearance in Caveman Inki, he appears after splitting a mountain in half. And when a hungry brontosaurus still tries to pick a fight with him, he gets tied up with his own tail for his trouble.