In Puella Magi Madoka Magica the Movie: Rebellion, Kyubey, despite being completly emotionless, he noticeably starts to become more frantic as his plans start falling apart. He even studders upon seeing Sayaka summon her witch form, and is shocked to learn that Sayaka and Nagisa are also part of the Law of Cycles. And then he and a mass of Incubators shout IT'S ILLOGICAL! in unison once their Isolation Field is destroyed. and finally he is reduced to genuine terror when Demon Houmura appears and his entire race is now under her rule. In the movie's final scene, he is nothing more than a broken mad being.
The last episode of the 2003 Astro Boy series could have easily been renamed from "The Final Showdown" to "Dr. Tenma's Breakdown." It begins in "Astro Reborn" with Tenma erasing Astro's memories to live out an idyllic life together as father and son. When that fails, and after going crazy on a pipe organ a la Phantom of the Opera, he takes over the Ministry of Science and demands one last meeting with "Tobio". When his We Can Rule Together speech to Astro then fails, he tries to commit suicide by destroying both himself and his old laboratory.
Mazinger Z: Dr. Hell had several breakdowns: The first of them happened in episode 3, right after Mazinger-Z defeated his first Mechanical Beasts, and he realized Juzo Kabuto still could surpass him and thwart his lifelong plans even after death. He destroyed all Mykene Humongous Mecha he had found, declaring them being uselesss, and he very nearly gave up right then, but The Dragon Baron Ashura convinced him to not forfeit his wolrd-domination dream. Another memorable one happened in episode 68, when finally he saw himself unable to triumph over Kouji Kabuto. He destroyed all of his newest Beasts, and swallowing his pride, asked help to Archduke Gorgon.
Great Mazinger: Great Marshall Of Hell — The Dragon of the second season — also had several of them at the end of series, mainly in the Gosaku Ota manga continuity. His expression and subsequent fit when Venus-A shot the flying fortress Mykeros down was particularly beautiful.
Zofis in Zatch Bell! suffers a really nasty one. Even after he gets his ass handed to him he remains defiant and tries to keep Koko's memories of her atrocities intact. Then Brago steps in and confronts Zofis with the fact that Zofis has been afraid of him from the beginning. He then threatens to hunt Zofis down and make his life miserable even after he returns to the mamodo world unless he erases the memories. At this point Zofis BREAKS DOWN CRYING WHILE LAUGHING INSANELY AT THE SAME TIME before finally yielding.
Captain Ginyu has an even BIGGER freakout when he reads Goku's Power Level. So much that, at least in the dub, Goku says to Jeice, "I think your friend's having a nervous breakdown!"
Frieza, upon seeing Goku transform into the Super Saiyan he feared for so long. He starts to become desperate once Goku gains the upper hand and really starts to lose it with each blow Goku deals him, resulting in an attempt to destroy Namek. It finally reaches its peak once Goku decides to call off the fight and states that Frieza already lost to someone who was "just a monkey" and tells him to live with the knowledge of defeat and flies off. Frieza snaps and had lost it so much he could barely think straight, resulting in attempting to kill Goku that leads to his own defeat by his own attack.
Later shown even quicker when Frieza shows up to get his revenge on Earth. Goku is MIA, and Trunks shows up instead. Frieza, not knowing who Trunks is, goes on long winded posturing about the backwater weakness of Earth and laughs at him thinking he can win... and when Trunks turns into a Super Saiyan, Frieza goes from gloating to absolutely terrified to completely enraged in seconds, going from standing around talking to frantically trying to blow him up.
Frieza, looking with horror as Trunks goes SSJ: It's- It's those eyes!
In Dragonball Z Resurrection F Frieza goes through this three times and with each one he loses much more of his sanity and by the end he's left screaming in horror when he is defeated and sent back to hell.
The episode in which Cell has his Villainous Breakdown was actually called "Cell's Mighty Breakdown" in English. In summary, after Gohan delivers two punches that make him drop to his knees, Cell decides to blow up the planet; only for Gohan to to fire an even bigger Kamehameha that almost reduces to him to nothing. This results in a Clipped Wing Angel that is easily beaten back to Semi-perfect form in one hit. From there, Cell decides to do suicidal bombing in order to win the fight, becoming completely unstable at this point.
When Cell returns as Super Perfect Cell you can tell he was going insane from being humiliated by SSJ2 Gohan. He was yelling nonsense, and had facial tics that only a demented madman would have. When he finally dies at the hands of Gohan, he can do nothing but scream "I AM PERFEEEEEECT!!!"
A much earlier breakdown contained an infamous shot of him screaming with his mouth wide open, which eventually became the infamous Lazer image.
Vegeta's former partner Nappa really loses it when Goku, a mere "third-class" Saiyan, starts curbstomping him.
After Majin Buu realizes he's been trapped in another dimension with no means of escape, he goes into a breakdown that results in a hole being ripped between dimensions from his screaming, allowing him to escape. A later breakdown occurs in the anime when he gets his ass kicked by Vegetto after gaining a stronger form: This time his screaming threatens to collapse the wall between dimensions entirely.
This only applies to Super Buu. Fat Buu is too carefree for a breakdown, while Kid Buu's one-track mind of destruction doesn't allow for breakdowns.
Light Yagami of Death Note lost his cool from time to time, especially right at the end, when he realized he'd finally run out of plans. The manga is especially an excellent example, as the would-be god realizes that he, whose pedestal was forged with so many deaths, does not himself want to die, and begs desperately for his life.
Parodied in this blog entry, which was also made into an animated gif and video.
He also gets a smaller one in episode 9, when L meets him at university and tells him, "I'm L." He manages to stay calm until getting home, where he screams in anger about how L got him, eventually giving his first psychotic laugh of the series.
There's also the deleted scene in the anime where Light stays in the graveyard after L's funeral, and remains composed until everyone leaves, whereupon he starts laughing madly, proceeds to crawl on top of his rival's grave and shouts, " What do you think of that, L? This is my perfect victory! That's right—I win!" with a crazed look on his face.
It really began in the very second episode when L first outfoxed him with a broadcast from a fake L. L on the other hand is rarely ever fazed.
Teru Mikami suffered one of these too. In the anime version, he committed an extremely painful looking suicide. The manga version was lower-key, but still present: upon realizing who Light truly is, he stares at him with the most distraught look and proclaims "you're not God!" He later commits suicide in prison out of despair.
Kyosuke Higuchi. Particularly in episode 23.
Lelouch from Code Geass degenerates into anger rather quickly during those few times when he is tactically outmaneuvered (typically when the white Knightmare shows up unexpectedly), in stark contrast to his usual smug and self-confident behavior.
When he discovers the identity of the Lancelot pilot. Lelouch was in position to terminate him at the time, but ordered a retreat when he was torn about what to do.
His reaction to the Euphinator incident. Once he gets back to somewhere private, he ends up sitting around crying about the fact that he accidentally made his second-favorite sister commit genocide, had to shoot her to stop the rampage, and then turned it to his political advantage.
The above instances could alternatively be Heroic BSOD's, depending on your interpretation of Lelouch.
Jeremiah Gottwald started this after he was stripped of his rank in the wake of the supposed "Orange-kun" incident. At the Battle of Narita, he nearly lets himself get killed while trying to kill Zero, and is seen after the battle gibbering crazily and fainting in the middle of a road.
Rolo goes through this in Episode 4 of R2. After Lelouch takes a bullet meant for his Knightmare, Rolo inadvertently joins the Black Knights, despite knowing his brother is Zero. Therefore, he can't capture C.C., which was his mission from the start. Lelouch plays the part of loving him as a brother in order to get Rolo on his side.
Ukyo from Samurai 7 maintains his Magnificent Bastard demeanor right up until he's attacked by Kikuchiyo in the last episode, upon which he snaps.
Dilandau in Vision of Escaflowne wavers between this and just being outright Ax-Crazy. In his first few appearances, he's merely sadistic. Once Van scarred his pretty face, he moved up to outright screaming psycho killer. Near the end, after Van killed his entire squad, he starts hallucinating and babbling and only snaps out of it long enough to slaughter a bunch of people.
Brooklyn the invincible world champion from Beyblade, after he was defeated by Kai who at the time was considered the biggest loser in the entire series. Not only that, but Brooklyn took the mental breakdown to the logical extreme: he convinced himself his defeat never happened, that everything was nothing but a nightmare, a bad dream that would end soon.
Makoto Shishio also has a breakdown after being hit with Kenshin's ultimate technique, though this is due in part to his badly burned body going over its 15 minutes limit of fighting, causing him to lose what little sanity he has.
Enishi Yukishiro also has a breakdown of epic proportions at the end of Jinchuu arc. When the image of his dead older sister Tomoe doesn't smile for him anymore, during his second fight with Kenshin... oh boooooooy, he loses it.
Yu-Gi-Oh! 5D's, in which The Rival, Jack Atlas, turns into a revenge-fueled lunatic upon finding out he technically lost to protagonist Yusei. Interestingly, Big Bad Godwin appears to be egging this breakdown on.
More recently, Placido more or less loses it when he realizes that Yusei has a chance of beating him, and went One-Winged Angel by revealing himself to be a cyborg and fusing himself with his D-Wheel to become a sort of motorcycle-centaur.
Later on, Aporia gets one during his fight against Jack, Rua, and Ruka. At first, he starts out as cool, calm, and in control, and spared Jack and Ruka just to piss Rua off. Later, when Rua intercepts an attack towards Jack, Aporia gets slightly pissed and attacks him, even if he could defeat one of the others. When Rua acquires his own Signer Dragon, Aporia becomes visibly angry, and moreso when Ruka destroys his Field Spell. He gets pushed over the edge when Jack destroys most of his Spells and Traps, and has a Slasher Smile when boosting his monster's ATK to 8300. He gets easily beat, falls to his death, and gets better.
Yubel has a similar breakdown in Yu-Gi-Oh! GX; after Judai finally gets it through her head that he doesn't share her twisted view of love, and is ready to commit to an Heroic Sacrifice to take her down, the normally-cool Duel Monster goes psycho and decides she won't omit herself and Judai from The End of the World as We Know It, after all.
Panik from the original Yu-Gi-Oh! suffers a huge one. At the beginning, he delights in putting Yugi through the same torture as Mai and countless other duelists, but at the end, he's reduced to a screaming, raving wreck as Yugi proceeds to push as many of Panik's buttons as he possibly can.
Kaiba himself suffers this whenever he loses or is on the verge of losing to Yugi. He even considers blowing up Alcatraz Island before the Battle City Tournament is up after he loses!
Kaiba *before Yugi commands Dark Paladin to attack*: YUGI!!! I WILL NOT BE DEFEATEDAT MY OWN TOURNAMENT!!!!
He suffers a similar one when Joey duels him after Yugi's duel. Using a clever strategy, Joey manages to destroy one of Kaiba's prized Blue-Eyes White Dragons, and then subsequently revives it onto his own side of the field, turning it against him. After seeing Joey, whom Kaiba always considered a second-rate duelist, is in command of his favorite monster and using it against him, he's livid.
Bandit Keith suffers one when Joey defeats him in the Duelist Kingdom arc, even with Keith cheating twice over (stealing Joey's entry card before the duel in an attempt to get him disqualified and cards hidden in his wristband during the duel). He screams that the duel didn't count by virtue of Joey not using his own entry card (revealing his machinations in the process), beats up Pegasus's guards when they try to drag him away, and pulls a gun on Pegasus himself (in Japan at least), demanding his prize money. He's tossed into the ocean for his trouble.
Team Kenya leader Victor of Medabots tournament arc managed to pull of The Stoic to an admirable degree, never once shifting from his slightly angry looking frown for the whole season. He continues this throughout the whole of the final, calmly and ruthlessly sacrificing his teammates and outright destroying two of Team Japan's Medabots without once raising his voice... right up to the point where The Hero expresses his intention to keep fighting despite having lost weapons, mobility and all of his armour. Then Victor laughs. Joker style. Along with his previously silent Medabot, who unleashes the hero's signature Finishing Move amid vitriolic ranting about the heroes abjectstupidity from the Slasher Smile sporting Victor. As one of the heroes notes, "Woah."
He gets worse when it is revealed that the entire tournament was merely a facade for the Rubber-Robo's real plan of triggering the Ten Days of Darkness again - the very Ten Days of Darkness that happened during Victor's childhood.
Takano's breakdown at the end of Higurashi: When They Cry. She loses it as the rest of the Yamainu are getting defeated by and surrendering to the protagonists and their friends and afterwards turn themselves in as they are placed under arrest. She refuses to give in, even when Okonogi eventually decides to accept defeat as well, and that's when she finally realizes that Nomura tricked her into helping her just to close up a company. Upon doing so, she snaps and starts running for the hills until she trips and falls. Just as it starts raining, she starts crying and tries to commit suicide by scratching out her own throat like some other characters did in previous arcs, just as the protagonists corner her. The group sees that she's been infected with the Hinamizawa Syndrome, and she attempts to shoot Hanyuu but Hanyuu easily dodges her bullet (since she is a god, after all). Just as Takano is about to be arrested, Tomitake stops the arrest and pities her for being a victim of the Hinamizawa Syndrome, and the group decides to cure her of the disease, having her sent to the hospital for curing. After the credits roll, things calm down a lot more for her when Frederica Bernkastel gives her a Happy Ending by preventing the deaths of her parents in order to change her destiny. This is a rather surprising and fitting fate for her.
And another one in Higurashi Kira Episode 2 during a battle with Oyashiro Rika and Trap Satoko alongside Ritual Tool Devil Nail Ripper. Takano becomes furious after Satoko transforms and helps Rika back up after which the two take her and Nail Ripper on together. The girls overpower Nail Ripper and Satoko creates a pitfall trap underneath its foot that it falls into, causing Takano to Freak Out and afterwards receive an Oh Crap! moment upon seeing the girls about to unleash their 07th Explosion attack which destroys Nail Ripper and sends Takano flying into the horizon, screaming "Sorry, Brother!" along the way before becoming A Twinkle in the Sky.
Kohane's mother in xxxHoLic has one that starts just after she suspects her daughter's medium abilities are fading. This culminates in a truly epic scene where she snaps, attacks Kohane, and then proceeds to beat Watanuki senseless for daring to intervene. All of this on live television.
In Xxx Ho LIC: A Midsummer Night's Dream, this happens to the dude who collects collectors when Yuuko walks towards him and is unfazed by anything he throws at her to keep her away. As she picks up the pace and begins to run, he gets even more desperate.
In Sailor Moon R, En had one of these in Episode 59 when Ail told her that Mamoru never really loved her. In response, she literally smacks him aside and begins blasting the two with energy, even blasting Moonlight Knight when he intervenes.
Koan (Catsy) goes on a blind, screaming rage after Rubeus confesses that he never loved her and her attempt at suicide with a time bomb was thwarted by the Sailor Scouts.
Rubeus himself had one of these, starting off when Sailor Moon and Chibi-Usa caused his ship to explode, and culminating when Esmeraude left him to die on said spaceship, ignoring his pleas for help. He goes from Evil Gloating to anger to begging over several minutes. And yes, he deserved it. It's even more noticible in the original Japanese.
Rubeus: ESMERAUDE! Help me! ESMERAUDE! (the ship blows up, killing him)
In S season, Eudial had one when the Holy Grail was revealed, flamethrowering the entire place with a deranged grin and laughing most of the way to get the Holy Grail. When Sailor Moon sends her out the window, she's really pissed, which leads directly to her death.
Queen Nehellenia, the Big Bad of Super S has one after being blasted by Sailor Moon's Golden Crystal causing her to turn into a hideous old woman and choosing to reactivate her magic mirror prison seal, rather than losing her beauty. Consequently, when she is released from the seal during the beginning of the next season she spends most of her time in this state raving about how she will make Sailor Moon and her friends suffer.
In the final of Witchblade anime Wadou slips into complete drooling insanity when his shady enterprises bring more disastrous effects than he could imagine. Looks like little backstabbing is one thing, but possibility of being obviously guilty in flattening half a city or so...
Berg Katse in Science Ninja Team Gatchaman spent his/her whole life being manipulated by Big Bad Sosai X, whom s/he worked his/her ass off to please. In the finale, however, X revealed that he intended to destroy the world and leave Katse behind to die with everyone else. Realizing s/he'd been played for a fool his/her whole life, Katse absolutely lost it in front of the Science Ninja Team and committed suicide by throwing himself/herself into the lava pit screaming "DIE, DIE, EVERYBODY DIE!!!".
Rau Le Creuset, the Big Bad of Mobile Suit Gundam SEED spent most of the series portrayed as a very calm and calculating individual. However near the end of the series when he comes face to face with The Protagonist Kira Yamato and longtime rival Mu La Flaga, he reveals his true nature as a raving Straw Nihilist and Omnicidal Maniac. He then proceeds to spend the final episodes of the series screaming and ranting about how Humans Are the Real Monsters and that everything must be destroyed until Kira finally shuts him up with a beam saber through the cockpit.
Azrael's horrendous one in the second-to-last episode. He had Natarle, Flay and the Bridge Bunniesat gunpoint to make sure they'd follow his orders while screaming like a maniac, beat up Flay when she tried to rebel, shot Natarle four times after she managed to get her subordinates away from him, and ultimately destroyed Fllaga's Gundam and killed him. It's almost a relief when Murrue uses the beam cannon of the Archangel to obliterate the Dominion. He gives a desperate "I always win". Natarle then tells him "you lose".
While Flay is more sympathetic, she has a rather tragic one in episode 28. By this point she has genuinely fallen in love with Kira despite her original plan, and as such has become even more confused than she was earlier. When she suspects Kira of pitying her she completely looses her composure, and breaks down sobbing while asking how he can possible pity someone like her (implying that she is filled with self-loathing).
The side-story Mobile Suit Gundam SEED Astray has Rondo Ghina Sahaku suffering one after Lowe Guele defeats him, despite the Red Frame losing the Gerbera Straight. It's especially shown when Ghina tries to shoot him in the back and is blocked by the Gerbera Straight's broken blade randomly floating by. Thankfully, Gai Murakumo puts Ghina out of his misery.
The sequel, Mobile Suit Gundam SEED Destiny has a major one in ReyZaBurrel. Having been defeated by Kira, and unable to avenge Rau, Rey comes to the realisation that he and ChairmanDurandal have been in the wrong. This culminates in him shooting Durandal and going out crying for his mother.
The former main hero, Shinn Asuka, essentially shambles into this trope in a very painful way. When we first see him, he's well adjusted with the worst thing he had was a chip on his shoulder towards ORB. However, as the series progresses, he loses more people he cared about either by death (like Stella) or rejection (like Athrun) and once Kira Yamato becomes the main hero once more, Shinn's nothing more than one big ball of anger, forged that way by Rey and Durandal and so lost in it that he loses sight of everything.
In the Mobile Suit Gundam Wing anime, the Treize Faction and the colonies have become White Fang and revolt against Tsubarov, and when his mobile dolls and Lunar Base are being destroyed by Wufei, he begins ranting about how "he is invincible" shortly before one of the explosions kills him.
Envy somewhat goes through this whenever some forces him to go into his true form, a small fetus-like lizard.
Envy's worst breakdown is when Ed, holding Envy's weakened form, reveals he knows what the source of Envy's hatred for humanity is: He envied their ability to care for one another. Enraged at having his motives perceived by a human he despised above all others, Envy tears out his own Philosopher's Stone and crushes it to spite Ed's mercy.
Central Command, with each General more or less losing it due to Roy and Olivier Armstrong's revolution defeating their forces and Father betraying them.
The Big Bad himself, Father, after succeeding at becoming a Physical God, rudely had 50 million bound souls torn out of his body by Hohenheim. The imbalance was enough that Father could barely restrain the power he had stolen. As he was forced to expend even more souls in an attempt to protect himself, his self-control decayed further until, at the end, he was a muttering, shambling hulk.
But Father's true breakdown occurs after his death; after confronting Truth and learning that he's no better then the humans he belittled, he's dragged into the Gate, asking in tearful screams what he should have done differently.
One of the less noticeable breakdowns happens to Wrath towards the end of his fight with Scar. After Scar has revealed that he has a reconstruction circle along with his destruction one, Bradley loses it and starts roaring at Scar about his use of alchemy despite it being abhorrent to the Ishvalans.
In the anime, Envy nearly breaks down after Dante sends Hohenheim of Light through the gate (thinking she killed him) but is talked into calming down when Dante promises to let him kill the Elrics. Even after killing Ed, he isn't satisfied. Upon being sent to the gate (thanks to Al using the stone and him trying to prevent it) and learning that Ed's father is still alive, he practically forces his way into the gate and loses it while transforming into a dragon in the process.
Also Dietlinde Eckhart, the main baddie from the movie for the first anime, near the end of the climax, goes into a tirade about how Ed's world is full of monsters when Ed gains the advantage. Ironically, she ends up turned into something of a monster on the the trip back to her world through the gate and shot as a hesult of her appearance.
Popo from Kaiba begins to lose it just as he wins. First, his mother's memory chip accidentally slips from his fingers and is destroyed, then he finds out his accomplice Cheki has had her personality wiped clean to become an obedient servant. Having lost these things precious to him and seeing the giant memory/Planet Eater plant coming towards planet Lala, he decides that letting it eat the world and achieving Instrumentality is the only solution.
Creed from Black Cat has one of these when Train goes to Creed's Supervillain Lair, pops in, saves Rinslet, then runs off, leaving everyone confused. Creed doesn't take it very well.
Isshiki gets one in RahXephon. After spending the entire show trying to play the Magnificent Bastard to prove that he isn't worthless he finally gets into a position where he can strike a definitive blow against the Mu... only to have it backfire spectacularly, leading directly to him losing his position and the Omniscient Council of Vagueness that he was working for denying ever having heard his name. He...doesn't take it well.
At the end of the first arc of Digimon Adventure 02, the Digimon Emperor starts having one of these as a result of trying to control Chimeramon. When he's finally defeated and learns the Digital World isn't some video game to win, he finally goes What Have I Done and turns back into his true identity, Ken Ichijouji. Think they're done there? It goes From Bad to Worse — minutes later, his partner Wormmon dies; when he goes back to the real world, he goes into a Heroic BSOD for two episodes.
Ken's breakdown is even more awful in the Japanese and uncut German version where most of the things he does after Chimeramon is yell a lot and whip Wormmon while it tries to explain the situation.
Triguncompletely reversed this during the climactic showdown between Vash and Legato. There, Vash... the good guy was in a mad panic, while Legato... the bad guy was remaining calm and reserved.
Played straight in the manga with Rai-Dei the Blade and Leonoff the Puppet Master. For the former, Vash manages to defeat him, the guy completely loses it and tries to kill Vash with one final attack only to be shot dead by Wolfwood. For the latter, even after he tries mindscrewing with Vash, Vash just calmly attempts to talk with him and starts reminding him of things from his past, revealing that he used to know Leonoff when he was younger. Leonoff can't take all these returning memories which he's apparently tried to dispose of before, and ultimately winds up killing himself.
During the first arc of Digimon Tamers, Yamaki has a long and escalating sequence of these, starting with angry rants when particularly stubborn "Wild Ones" resist deletion up to a full-on, possibly partially insane breakdown when the Juggernaut program doesn't work as planned, including choking a kid and stumbling off yelling angrily to himself in proud Lovecraftian fashion. Surprisingly, he does not have one when he's fired after Hypnos collapses, instead beginning a Heel–Face Turn that results in him becoming a staunch (and largely sane) ally.
Lucemon from Digimon Frontier generally shows no emotion except cold disdain—but he loses it on the two occasions he's outmatched by Susannoomon. The second time is particularly extreme, as he's reduced to screaming about his "utopia."
Gaara, whose sand provided him with such perfect protection that he'd never been hit, much less felt physical pain (up to a certain point, though), is stabbed in the shoulder by Sasuke. Gaara wonders what that warm, wet stuff is and then goes nuts when he realizes it's his own blood.
He has an even bigger one during his final battle with Naruto later that day. For all his life, Gaara's been driven by his hatred and rage, and in the final decisive clash, Naruto's love for his friends gave him the power to overcome Gaara. Realizing that his entire philosophy was wrong makes Gaara lose it completely, screaming while Naruto continues to crawl towards him. Despite this, it's Naruto's understanding of his history that helps him let go of his hate at last.
Itachi has a rather frightening one during his fight with Sasuke. When he finally reveals his reason for sparing Sasuke, he flips out into a maniacal, almost psychotic scream session, sharply contrasting his usual stoic behavior. Itachi implied afterwards that this was not a breakdown, it's how he truly is on the inside. It's later revealed, however, that the entire breakdown was purely an act.
Sasuke himself cracks during his fight with Kakashi after meeting Team Seven again. He gets uncharacteristically mad at a "low-life" like Kakashi merely possessing a Sharingan, then claims that the laughter of the villagers in his memories is ridicule because they're ignorant of Itachi's sacrifice: he'll shut them up by killing everyone in Konoha. He goes completely Laughing Mad (see it here).
Deidara gets pretty unhinged when he realizes that Itachi's Sharingan is more artful than his bombs, and he tries to kill Sasuke by blowing himself up at the end of their battle.
Filler Villain Fuka has one every time Naruto manages to hurt her or damage her hair.
When Kabuto was attacked in Part I we see his eyes go bloodshot as he reveals a bloodthirsty side. Also, after Orochimaru died, Kabuto had an existential crisis, but he claims that the person who inspired him to continue was Naruto.
During Kabuto's fight with Sasuke and Itachi, Kabuto has some more of these. Confident in his beliefs and victory, he begins to shed tears when the Uchiha brothers fend off his attacks, and during his counterattack tearfully declares that a genius in everything, like Itachi, wouldn't understand his desire to find his true self: no one would stand in his way.
Hellmaster Phibrizzo from Slayers NEXT. When his plan to have Lina cast the Giga Slave and destroy the world backfires due to Lina being possessed by the Lord of Nightmares, he completely flips out, eventually screaming out "I WANNA BE DESTROYED!". His wish is granted shortly afterwards.
Valgaav from TRY inverts this trope. At first, he's fueled by vengeance against both Lina and the Dragons, with the anger and psychosis you'd expect from such a motive, but after merging with Darkstar, he reveals his new plan to remake the world with an eerily calm demeanor.
Almost every One PieceBig Bad has one. Kuro, Don Krieg, Arlong, Wapol, Crocodile, Eneru and Moria all have epic breakdowns while fighting Luffy.
So far, the only major enemy that Luffy has actually defeated to NOT have a breakdown was Arrogant Kung-Fu Guy Rob Lucci. He only had time for an Oh Crap!.
Moria's breakdown came at about the same time as he used Shadows Asgard.
Elite Mook Blueno as he fights Luffy during the Enies Lobby arc. Blueno had previously defeated Luffy on Water 7 along with the rest of CP9, especially since Luffy couldn't at first overcome their special martial arts. When the two face off again (with Blueno by himself no less), not only does Luffy get past his strong defense, he can even keep up with him. Blueno keeps his composure through that, seeming shocked and impressed that Luffy is that good, but he's still in control. Then Luffy uses Gear Second, and the breakdown begins as he is unable even to dodge, finally ending where he tries to stand up to a strong attack. Once it hits, he looks like he has a smug grin on his face from withstanding the impact...only to drop a second later, out cold.
Part of the reason he's so horrified at what Luffy is doing is because this particular CP9 generation is the strongest one yet and has never lost a fight. Blueno had clobbered Luffy twice and stopped the Straw Hat Pirates several times already to where he feels it's a routine. As he doesn't know what it's like to not curb stomp everyone in his way, let alone run out of options the moment the match had begun, he momentarily loses all coherent thought. The whole squad is in such disbelief that Luffy was victorious that some of his comrades pretend it didn't happen and the others decide to accept hasty (and incorrect) conclusions of what just happened…though they're probably right on the count that spending five years as a bartender didn't help with his fighting skills.
While the New Fishman Pirates were never entirely sane in the first place, they go completely nuts when Luffy defeats Hody. They start killing their own men as "sacrifices" for their hatred towards humans.
Hody Jones, leader of the New Fishman Pirates, undergoes a physical breakdown to go with the mental one. Near the end of his fight with Luffy, Hody's face seems to degenerate, becoming less human.
Donquixote Doflamingo is an interesting example. At first, it wasn't Luffy, but Law, who began to tweak Doflamingo by capturing Caesar and gave him the choice of either giving up his title as a Warlord or face the wrath of Kaido of the Four Emperor's when Doflamingo couldn't provide him anymore artificial devil fruits without Caesar's help. Doflamingo eventually managed to cool down after thwarting Law's plan and capturing him, but then he suffered another one after losing control of his kingdom thanks to the Straw Hats. His final breakdown followed the series' formula when Luffy finally squared off against him and gave him an epic beatdown.
In GUN×SWORD, the Claw's dream is delayed at the 11th hour by Ray's Heroic Sacrifice, leading to his claw twitching for a full episode. When Van puts his dreams of Instrumentality down for good, he goes completely off the handle.
This happens to Griffith in Berserk when Guts defeats him in one single stroke to earn his freedom. Guts' desertion marks a turning point in Griffith's life and ambitions and everything falls apart for Griffith from there on, making it an apt breakdown.
Johan from Monster has three of these — one after finding a Bonaparta children's book that helped mess him up as a kid, and the other after he realizes that his memories are actually Nina's, the latter leading to the climactic scenes in Ruhenheim. Then he has a freakout at the climax when his sister determinedly interrupts his Kill Him Already-moment with Tenma to Carebear Stare at him just as he's getting into his Breaking Speech stride. "I am too irredeemable! Now shoot me in the head or the kid gets it!". Given what he is, these make him even scarier.
Peter Capek is an even more straightforward when he discovers that [[spoiler:he and his entire underground neo-nazi movement were being manipulated all along by Johan, who never cared about their promises of power and has started to kill them all one by one. Capek rapidly begins to lose it, to the point of killing his chaffeur out of fear - which causes his former bodyguards to shoot him down in reprisal.
Harry McDowell of the Gungrave anime is always completely calm and collected, no matter how bad a situation he's in, and never fires a weapon himself, until Brandon Heat, his best friend points a gun at him. Harry draws his own gun, fires at least five shots into him, then rams the barrel into his eye and fires a sixth. Later on he gets two other breakdowns as he's trying to deal with the fact that he killed his best friend whom he's trusted and relied on since they were children and whom he wanted to stay by his side.
Plays out a little differently in the game's storyline. Harry just gets a punch to the face because he had plans to manipulate Maria into being Brandon's wife, something that Brandon would never do. Harry's also oddly calm when Grave/Brandon confronts him at the very end of the game. With all of Harry's lieutenants and monsters destroyed, he simply accepts his defeat and allows Grave to kill him.
The Anti-Spirals (represented by their avatar the Anti-Spiral King) of Tengen Toppa Gurren Lagann are archetypal inhumanly calm and dispassionate Scary Dogmatic Aliens. Until the last episode. During the Final Battle the Anti-Spirals unleash thousands of years worth of repressed emotion and Hot Blood, ranting about the sacrifices they made to protect the universe and screaming that the protagonists are idiots who don't realize that their actions will lead to the end of everything.
It's actually a vital plot point if you look at it right. Both Lord Genome and the Anti-Spiral are very calm and confident, Smug Snake levels on the part of the Anti-Spiral. When the heroes manage to fight them face to face, they go completely Hot-Blooded and proceed with the ass-kicking. The reason it's a plot point is because the Anti-Spirals, and by extension Lord Genome, were trying to suppress hot blooded badassery.Lampshaded on the part of Lord Genome and foreshadowed for the Anti-Spiral when Anti-Spiral Nia says "Not even Lord Genome could suppress the Spiral instinct."
Cytomander also loses a fair chunk of his self-control during the Battle of Teppelin, such as cackling like a maniac after Simon unleashes a drill Macross Missile Massacre.
In Fruits Basket, Akito Sohma has a rather fragile grip on reality and thus it takes little to shake her up. A first breakdown comes after Kureno is freed from the curse, causing her to go from a scared but mostly kind child to full-on possessive and clingy, beating and locking up the other Zodiac members to keep them from "leaving" too. A second one comes towards the end of the series, after Momiji is freed, panicking her again to the point of nearly stabbing his mother with a knife. This breakdown is only intensified when Hiro is freedin the middle of the attack, leading Akito to stab Kureno in the back and then go off in a delirious state to attack Tohru Honda, who she blames for everything. However, Tohru manages to actually get to Akito and talks to her kindly... and after Tohru almost falls victim to Death by Falling Over in the middle of their confrontation, Akito finally realizes what a fucked-up bitch she is and has a Heel–Face Turn..
Akito's mother Ren, who is just as screwed-up, has a breakdown of her own when she learns that Shigure only slept with her and showed any interest in her because he was in love with Akito and thought Akito would look more like her, had she been raised as a girl and not as a boy per Ren's selfish demands, thus causing her to enter Akito's room with a knife and demand that she hand over a box which supposedly had something of Akira (Akito's late father)'s in it. It's empty.
Ulquiorra gets a brief one in his fight with Ichigo. After his first release and curbstomping Ichigo, he loses his usual composure when despite seeing the difference between their powers Ichigo refuses to give up.
In chapter 385, Tousen loses his composure and goes on a tirade explaining why he chose to betray Soul Society. To add to the effect, Tosen's blank Hollow mask cracks open in a manner that resembles teeth. And in the next chapter, he goes completelyinsane after his Resurrecion grants him eyesight. This proves to be his undoing.
After being hit with a second bankai from Soi Fon, Barragan Luisenbarn loses all composure and goes on a rant that covers every facet of this trope. He proclaims himself to be a god, orders his opponets to bow before his might, and keeps muttering "You insects!" over and over again. It only gets worse after he starts to evaporate, culminating in him throwing his axe at his own boss!
Aizen spends most of his screen time being invincible, and talking about how invincible he is, while never raising his voice or getting mad. Once the Deicide Arc rolls around, he's defeated everyone that's fought him, and is on his way to create the King's Key and destroy Soul Society. Then Ichigo returns, having finished his training to use the Final Getsuga Tenshou. Ichigo manhandles Aizen with nothing but his physical strength, and Aizen loses some of his composure. Aizen transforms into monstrous form after monstrous form, yelling about how much better he is than Ichigo, and losing it more and more as they fight. Once Ichigo effortlessly destroys Aizen's perfectly chanted Black Coffin Kido spell, he cracks completely, and starts ranting at length about how he's the perfect existence, and that he can't be stopped by Ichigo. Then Ichigo blasts him with his Mugetsu technique, Aizen is rejected by the Hougyouku, and Urahara Kisuke's Sealing Kido activates, sealing him in an energy tree as he screams that he's the only one with the right to change the world. He's cut off mid sentence, and is next seen being sentenced to 20,000 years of imprisonment by the Central 46, since they can't execute him because he's immortal due to the Hougyouku. It's all very satisfying, as Aizen is The Scrappy to a vast number of Bleach readers.
Also Szayel Aporro Granz, who starts out smug and confident in his superiority. When Mayuri starts messing with him, however, he throws a temper tantrum and starts swearing a lot. He's also breaking down shortly before his death, begging for Mayuri to hurry up and kill him, but then again from his perspective, he's been frozen in place with a sword slowly piercing him for a MILLENNIUM by then.
Zommari probably had the biggest one out of all the Espada, he comes off as being the most composed of the group, going on long tangents on how his opponent cannot beat him, believing his powers is enough to stop him from moving. When he attempts to have that man's sister to be killed, he gets tired of this game and simply casts a Kido to paralyze her. Zommari, more explict in the anime, immediately loses it and demands his target to move; immediately following a 360 attack by his enemy, causing him to use his full power while proclaiming loudly, even though it fails miserably. The Next chapter has him in Madness Mantra mode, going on a speech about What Measure Is a Non-Human?, ending with a clear Villainous Breakdown of him praising the Big Bad as he dissolves.
Kenpachi's clear enjoyment of what appears to Nnoitra to be a losing battle starts to strongly unnerve Nnoitra. As Kenpachi continues to laugh and enjoy himself, Nnoitra descends into raving and swearing at him. Eventually, this psychological edge causes Nnoitra to be too shaken to think to defend himself when Kenpachi finally goes for a killing strike, crippling him in one blow.
In chapter 477, Tsukishima, who's normally calm and composed, has a Freak Out moment following Riruka shielding Ichigo and Rukia from his attack that was meant to kill them. He gets this look on his face and screams at her to "MOVE!!!" In chapter 478, we see Tsukishima acting deeply upset over Ginjou's death and having another Freak Out moment.
In chapter 272 of Mahou Sensei Negima!, Kurt Godel loses some of his composure when Negi reveals that he knows that the Magical World is falling apart. Negi then accuses him of betraying the ideals of the people he looked up to in his youth namely Arika and Nagi. Godel gets pissed, calls Negi a "little boy who's too smart for his own good", and decides to force Negi to be his pawn. It fails.
And in chapter 298, Fate, who's normally coldly Stoic visibly trembles with wrath and looks upset when Negi declares that he will prevent the future in which the magical world collapses from happening.
FLCL has a strange one (Anyone surprised?) when Naota reveals that he's absorbed the powers of Atomsk... it's Haruko that snaps, who immediately grabs her weapon (read: guitar) and lunges at Naota, screaming "THAT POWER'S MINE!!!"
Yokoya in Liar Game could lie, deceive and bribe his way through any situation. That is, until he met Nao and Akiyama. At the end of the Second round, he managed to profit greatly from the game, when everyone else had just managed to pay off their debts and gained nothing. He began gloating to Akiyama that he had lost, when Nao of all people mentioned how Yokoya had contradicted his earlier philosophy of dominance. Instead, he had turned to tricks to profit and unknowingly had three traitors on his side. "Even though you made the big money, Mr Yokoya, you lost the game to me."
In the Pandemic game, when he tried to bribe money to one of his teammates who trapped himself in the examination room, his teammate continually kept demanding more and more money, until Yokoya visually lost his calm demeanor and began violently kicking at the door ... only to find out that it was Akiyama in the room the whole time and who he was slipping money to.
Almost every single person who's faced down Alucard suffers such a breakdown at the end of their fight. Like Rip Van Winkle (whom you could almost feel sorry for) and Luke Valentine (if only for Alucard's Pre-Mortem One-Liner: "I'm a dog? Then you're dog food." Followed by mastication.)
Zorin Blitz gets seriously freaked out when she learns just why she shouldn't have fucked with Seras. She was all confident while she was pulling a Break the Cutie tactic on Seras, mind raping and maiming her, killing Pip, and referring to the dead Pip as an insect. Seras then snaps and Zorin had a permanent Oh Crap! expression on her face up until Seras kills her by grating her face against a wall until the only intact part of her face left is an ear.
Enrico Maxwell has one during his assault on London, it rose when Alucard summoned his familiars and massicared his armies, and it went on max level when Anderson breaks the armored glass protecting him from Alucard's familiars. This is followed by him being Impaled with Extreme Prejudice.
In fact, there are probably only three villains who avert this trope: Jan Valentine (who goes out laughing his ass off), the Captain (who goes out the same way), and the Major (who just wanted constant and everlasting war, regardless of who won or lost).
Daniel J. D'Arby's epic breakdown in Part 3 of JoJo's Bizarre Adventure. Jotaro beats D'Arby in a game of poker by messing him up through sheer bluffing. D'Arby is an expert gambler, had the whole game rigged to his advantage, but ultimately lost to Jotaro's extreme poker face and his own immerse fear that if he loses, he must reveal Dio's secret, which is likely to get him killed.
From Part 2, Esidisi invokes this by crying like a spoiled brat once his hand is cut off to calm himself down and unnerve Joseph. He suffers a real one once Joseph manages to out gambit him, leading to a futile Clipped Wing Angel in an attempt to take him with him.
Aureolus Izzard from A Certain Magical Index goes from a calm, Magnificent Bastard to a murderous lunatic when Stiyl and Touma inform him that his complicated plan to find and trap a vampire, then force it to turn Index into a vampire in order to save her life is completely unnecessary because Touma already saved her. He gets even more upset when Stiyl questions why he needed to find and trap a vampire in the first place if he has Reality Warper powers, he could have just summoned one or even turned Index into a vampire himself. Then, he completely loses it when Touma acts like Aureolus chopping his arm off means nothing to him and slowly advances on him, laughing like a crazed lunatic and giving a "The Reason You Suck" Speech. In a blind panic, Aureolus screams, "He's a monster!" and has just enough time to go Oh Crap! before his Reality Warper powers turn against him and cause a dragon to emerge from Touma's arm stump, which finishes him off.
Accelerator also has one of these (not sure if other moments really count for this) after Touma slaps his hand away, something that has never happened due to his vector control ability redirecting any and all attacks or block attempts.
Happens to Aleister Crowley, the biggest of the Big Bads, and most chessy of The Chessmasters, when the otherwise meaningless and insignificant level 0, Shiage Hamazura, manages to beat the level 5, Shizuri Mugino, using nothing but his own strength and determination, completely going against all of Aleister's plans. He orders his execution, but Shiage still somehow manages to live on, making life even more difficult for Aleister.
Awaki Musujime has one when Kuroko gives her a breaking speech about exactly what is wrong with her as a person, and exactly why everything is her fault, not the fault of her powers or her circumstances. She goes so crazy for a moment that she collapses the entire building on Kuroko (who barely escapes alive thanks to Touma and Misaka showing up).
Daemon Spade loses it when Tsuna gains the combined powers of the Vongola and Shimon rings. He becomes a screaming lunatic futilely lashing out in rage and denial. The breakdown is reflected in his appearance — his once bishonen form becomes a warped and hideous mass Body Horror.
Soul Eater is fond of these, since most of its characters aren't exactly stable.
Dark Magical...Person Crona is constantly on the cusp of a nervous breakdown anyway, but goes absolutely ballistic when Maka connects with their psyche.
Giriko has one following Arachne's death. And later, he follows it up with an even bigger one. In fact, he gets so angry that his soul explodes.
Kishin Asura has these constantly in the anime, due to his overwhelming terror at anything he doesn't understand, but there needs to be a special mention for the absolutely SPECTACULAR one that he has in the final episode.
Iwao Washizu from Akagi completely breaks down and briefly goes catatonic when Akagi manages to outperform him in their epic Mahjong match. Akagi personally has to talk him into continuing their game, and gives himself a disadvantage for the next round.
In the second-to-last episode of Shaman King, Hao gets a huge Villainous Breakdown when Yoh regains his soul and his consciousness to the joy of his friends and his fiencee Anna - leading Hao himself to lose his cool and get really mad as well as go Ax-Crazy, to Opacho's upset.
Opacho: ...I don't understand. I thought we were friends... (walks away sadly) Hao: Hah... hahaha... HAHAHAHAHAHAHA! Opacho's gonna miss out on all the fun! HEAR ME NOW, SPIRIT OF FIRE! (Spirit of Fire appears) REGENERATE, AND ARIIIIIISSSEEEE!!! Devour him! (Spirit of Fire lunges at the Great Spirits and starts absorbing their energy)
Moo in Monster Rancher Episode 47. During his final attack on the Searchers, he is completely overcome by the evil of his soul, and completely goes berserk, even destroying many of his own men. In the next episode he is finally destroyed.
Shugo Chara!: Nikaidou, after capturing Su (And, previously, both of Amu's other Charas, although, by that time, they had been freed), seems to become more, and more unhinged, constantly ranting about his obssession with success and societal promotion, although whether or not that was him trying to (Thankfully, failingly.) "convince" him - self to not embrace his past Dreams is left un - clear.) and typing furiously upon his computer while once hitting his desk hard. His only moments of knowingness come when Su speaks towards him, trying to convince him to let her out to clean his room and make him a new cup of coffee, rather than escape and, more noticeably, when she (Albeit inadvertently.) reminds him of his own Dreams. An odd case within the fact that only one protagonist (Su, who is being held hostage.) ever gets to see most of it within action. And his face. Good God, his face. Also becomes completely subverted during The Anime's finale/conclusion of the manga's third arc: Gozen breaks down, but it's not at all villanous: Goxen has been revealed to be Hikaru, the boy that Amu encountered (Within an, at times, ''very disturbing'' fashion.) before - hand, and he is crying through - out years of repressed sadness due towards his extraordinarily strict upbriging, which the return of his Heart's Egg towards him lets completely out, thus stopping his usual (albeit false) extraordinarily unfeeling temperament.
Throughout the Cowboy Bebop episode "Pierrot le Fou", Tongpu/Mad Pierrot is set up as a psychotic and seemingly invulnerable assassin who can stop bullets with the greatest of ease. However, when Spike manages to embed a knife into the guy's thigh, the up-until-that-point cold-blooded killer is reduced to a bawling mess thrashing on the pavement and crying for his mommy. The earlier establishment that his mental state and powers are the result of genetic engineering experiments performed on him does serve to make this childish tantrum not seem so out-of-the-blue.
Minor character Kashiwara has one in the first episode of GunBuster. After Noriko "Wipe Out Girl" Takaya is chosen for a position that she felt should have been hers, and Coach doesn't do a damn thing to explain himself, Kashiwara tricks Noriko into a mecha battle - up to this point, Noriko's nickname of "Wipe Out Girl" was given to her for a reason. As Kashiwara keeps kicking Noriko's ass, she goes on a brief rant about how the latter girl has no skills or talent, and her epxression is truly frightening. And when Noriko turns off her monitor on a desperate gamble, then Kashiwara goes completelyapeshit and evidently tries to kill her. Fortunately, though, Noriko responds withher legs.
Sakura Gari: Sakurako, Souma's Yandere sister, suffers a massive (and heartbreaking one near the end. S/he's actually a boy named Youya, desperately lonely and unstable, and s/he ends up commiting suicide when s/he thinks s/he's killed Souma. But not before... after having locked Souma and Masataka away in a burning building, s/he stumbles in Lord Saiki's bedroom, whispering "Father... Sakurako has always wanted to see you...", then starting to chop up everything in sight with his/her trusty katana, crying and screaming "Why was I born? Why am I here? Why do I exist, Father, WHY?!" When s/he stops and realizes that Souma might be dead, s/he screams in horror, lets go of their Weapon of Choice and then runs under the cherry trees... Few later, we find him/her dead, his/her wrists slit open and their lifeless body inside the pool. And Souma bawls his eyes out with his/her lifeless body in his arms.
Post Haguro's death, Ryuuko just lost what little bit of sanity she had left (and considering how Ax-Crazy she was there wasn't much left), wandering on the streets and selling her body in utter disbelief now that she lost Haguro and couldn't get Inugami.
Akuha at the end of chapter 53 breaks down laughing and crying out of insane jealousy after she sees Moka with Tsukune.
Kanamori has two in the manga Higanbana No Saku Yoru Ni. The first is when Marie Moriya, the girl he's been molesting during his "supplementary lessons" with her, threatens to tell others about their supplementary lessons, he snaps, and strangles her to death. The second breakdown was when he failed the three rules about Mesomeso, and Marie becomes Mesomeso, and is about to kill him, he breaks down, and told her that he always loved her. She tells him she loved him too, and gives him the Kiss of Death.
And later, Deep Blue gets this when Ichigo reaches out to Masaya, who apparently starts fighting back against the aliens' leader from within him. The more Masaya fights back, the more Deep Blue loses his composure. And he gets even worse when he finally realizes what is happening to him, and eventually gets held in place by Masaya much to even more of his agitation. His breakdown gets more and more intense until Ichigo becomes forced to defeat them both in order to set her beloved Masaya free, which is a rather nice end to Deep Blue.
The Dark Precure goes through this near the end of Heart Catch Pretty Cure. When she first appears, she's calm, collected and a walking can of Curb-Stomp Battle. However, once Yuri regains her Heroic Resolve and returns to action, she starts to steadily lose her composure, especially since Yuri's finally dumped her baggage and is fighting clearer. By the time of the final battle, and hopped up on a power boost, she's gone completely berserk, and all she wants to do now is just kill Yuri so she can have their father, Professor Sabaaku (a.k.a. Yuri's father Mr. Tsukikage, brainwashed by Dune), accept her as his only daughter. Though after she is fatally wounded by Cure Moonlight, and a now-freed Mr. Tsukikage accepts her and Yuri as his daughters, she seems to finally let go of her rage and hatred as she dies.
Big Bad Dune soon follows. When we first seem him, he's a Smug Snake who gladly wipes the floor with the other Cures and turns the Earth into a desert. Once Yuri finally drops the rest of her baggage, restored to full power and her and Tsubomi are reunited with Erika and Itsuki that things start going south for Dune. When he's nearly purified by the Heartcatch Orchestra, he flips out, grows to massive proportions and starts punching the Earth, declaring that nothing can defeat the hate in his heart.
Darcia the Third from Wolf's Rain has several in varying degrees, but the biggest comes in the last few episodes, where he kills the main cast so *he* can be the one to open Paradise. His last moments are spent cackling madly, with his wolf form managing to look rather insane as well.
Chaka in Black Lagoon is an arrogant small-time Yakuza with delusions of grandeur who tries to make a name for himself by kidnapping Yukio, the new head of the Washimine clan. When Rock, Revy, and Ginji storm his hideout to rescue her, he reacts with his usual bravado. However, he's quickly subjected to a Humiliation Conga. The cracks start to appear when Rock snatches his hostage from right under his nose, leading him to shoot his own henchmen in the back when they try to abandon him. Things get worse when he challenges Revy to a duel, only for her to dropkick him in the face and declare him Not Worth Killing. Finally, when Ginji chops off his hands and knocks him into a swimming pool to drown, he's reduced to thrashing around and shrieking impotent death threats.
Joker of Smile Pretty Cure! suffers a major one. At this point, it seems like he's achieved some sort of victory, gathering tons more of negative energy to revive Big Bad Pierrot. And the icing on the cake, he's created his own group of Psycho Rangers, the Bad End Precure, and sends them to deal with the girls for good. Things fall apart when he realizes that the Miracle Jewel he sought was just a fluke - it was just the egg form of Queen Candy. It goes downhill once the girls are able to overpower their twins and return to the real world that Joker flips out, revealing he's only doing this because he wants to sow chaos, that he has no real purpose. At the very end, a batch of the Bad End ink falls on top off him and he "gleefully" disappears and is absorbed into Pierrot.
In Girls und Panzer, when Alice finds out that Oorai has discovered that they were intercepting their radio transmissions and is using that tactic against them, she breaks down and starts ranting about various things, such as a boy who won't notice her feelings, the supposed superiority of the Sherman Tanks, and how if Oorai is getting shut down, it should be shut down immediately. She briefly regains her composure when the team captain sends reinforcements, but when the team loses anyway, she breaks down again, especially when Kay states she wants to give her a talking-to.
Episode 11 of Canaan has Liang Qi suffering severe Sanity Slippage (not that she's ever been sane to begin with) as a result of her "nee-sama", Alphard, abandoning her. When Cummings tries to get her to see reason, she shoots him in the leg and then gives him the beating of his life, all the while ranting loudly about how she will destroy anyone and anything that gets between her and her "nee-sama." Then Alphard battles her hand-to-hand, and Liang proves Too Kinky to Torture, begging for more pain from her. When Alphard's attention turns toward Canaan blasting up the soldiers raiding the base, Liang Qi loses it big-time. She breaks into Cummings's lab and takes a dose of the Ua virus in a mad bid to give herself synaesthesia like Canaan. But since Liang Qi doesn't have the genes to handle synaesthesia, she suffers horribly both physically and mentally. Then Alphard shows her the card that Liang wrote in Siam's name, revealing that she knew all about her plot to "rescue" her, and revealing that Siam never called her Alphard...but Canaan. This results in Liang Qi losing it completely, becoming so far gone that she doesn't even recognize her own reflection in the mirror, believing that it is Canaan staring back at her. It ultimately falls to Cummings to deliver a Mercy Kill.
Carnival Phantasm'sWacky Racing episode had this happen to Gilgamesh when he realized that Shirou and Saber were finally catching up to him, Archer, and Rin as they were nearing the finish line. The arrogant, prideful god-king immediately lost his temper big time, screaming the word "bastard" several times and calling Shirou and Saber "goddamn brutes" as the three teams of racers lined up neck and neck and approached closer to the finish line.
Adachi from Persona 4: The Animation immediately starts freaking out when he realises that the kids he's fighting aren't as pathetic as he expected, and also that they're rejecting his philosophy, he almost kills himself too, but then he gets possessed by Ameno-Sagiri
Attack on Titan plays this for drama, showing just how terrifying a broken villain at the end of their rope really is.
When confronted and exposed as the Female Titan, Annie's calm shatters and the body count rapidly begins to rise. Unlike in the previous confrontation, Annie is clearly desperate and begins to flash back to their Freudian Excuse while delivering a vicious beatdown to Eren. Rather than attempt to capture him, however, she makes a final desperate attempt to escape by Wall Crawling up Wall Sina. When this fails, she begins to weep and seals herself away in a Crystal Prison. The battle leaves the city in ruins, with many wounded or dead among the military and civilians alike.
After The Reveal, Reiner was already suffering from Sanity Slippage but made no effort to attack the heroes. This changes completely once Erwin manages to rescue Eren, seriously wounding Bertolt in the process. Cue the Armored Titan picking up and hurling other Titans at the fleeing soldiers with Improbable Aiming Skills, cutting off their escape. Mikasa and Jean are both injured, while many soldiers are killed in the ensuing slaughter. Armin is horrified by the enemy's sudden reckless behavior, wondering if he even cares anymore if Eren ends up being eaten along with everyone else. Without Eren's Eleventh Hour Super Power, everyone would have ended up being devoured.
In episode six of Tenchi Muyo!, it seems that Kagato is close to victory: Tenchi and Ryoko are helpless, Ayeka and Mihoshi are trapped in another dimension with Washu and the Juraian ship Tsunami is being drawn into the Souja with the namesake Goddess and Sasami being dragged in for the ride. Then, Tenchi decides to follow up on some advice Tsunami gave and, when Kagato attacks Tenchi again, he's stunned to see him with three Light Hawk Wings. He's quick to point out that there's no way Tsunami could be giving him her power until he realizes the true horror: this isn't Tsunami's doing.
The Enterprise scientist in Chapter 3 starts out very confident in the security he has got for his secret lab, as he tells Faceas Clay through a phone call. This confidence vanishes just as Hiryu and Cain make quick work of his men, making him jump on the phone to ask for reinforcements moments before both striders confront him. But the real breaking point comes right after Hiryu destroys the Zain Terminal, which he treated as his child: he goes Laughing Mad, mocking Hiryu and Cain that their efforts are futile since the terminal they destroyed was but one of millons and finally burns to death while fanatically praising Faceas Clay.
Vice-Director Matic in the final chapter. Ever the Smug Snake, Matic corners an exhausted Hiryu after he murdered Clay (as he wanted), explains to him all his plans to take over both the Striders and Enteprise, and is about to execute Hiryu when Cain comes to the rescue. From there, it's all downhill for him: he fights an injured and weakened Hiryu, but backs away when Hiryu adamantly refuses to go down, then finds the Striders he thought were his lackeys don't follow his orders, and then Director Kuramoto (who he ordered his execution) was not only alive, but on to his treason. Cornered, he breaks down and threatens all present with a bomb, only to be Impaled with Extreme Prejudice seconds after by the main Zain computer he desired for so long.
Nazi soldier Adolf Kaufmann, among all his nasty deeds, spends almost the entirety of Adolf looking for the documents that prove Hitler's Jewish origins in order to destroy them. When he finally succeeds in finding them, he is immediately informed of Germany's defeat and Hitler's death. Having realized that he lost a good chunk of his life in going after what are now useless pieces of paper, he starts laughing madly and then desperately crying.
Impressively averted in Binan Koukou Chikyuu Bouei-bu LOVE!. Kinshiro Kusatsu, the leader of the Terrible Trio of evil Magical Boys, is arrogant, elitist, hyper-pretentious and, under his cool cover, more than a little emotionally unstable. He's an absolutely prime candidate for a Villainous Breakdown of the first order, and he does go on an Evil Makeover-fuelledRoaring Rampage of Revenge in the second-to-last episode. Come the finale, however, he finds that rather than being groomed for World Domination, he's been featuring in an Immoral Reality Show, that the Mentor Mascot he swore an oath to follow has been using him as a patsy, that his varied palette of emotional distress has been used for entertainment, and that despite all of this, he's still expected to fight for the cameras. Instead of taking the final plunge that seems so likely, his reaction is a very quiet and dignified refusal.
The realization that he is alone, his underlings are defeated, and everyone else in the guild are risking their lives to stop him completely shatters Laxus' composure. Unfortunately, instead of collapsing, he goes into Unstoppable Rage.
The Oración Seis seems pretty prone to this. Both Racer when Lyon figured his powers out and Angel when Gemini disobeyed her in favor of Lucy's kindheartedness towards celestial spirits have broken so far. Brain has a pretty good one here too, with eyes bulging out and everything.
Edolas!Erza when she's screaming about how Edolas will suffer without magic. Like Laxus, she also goes into Unstoppable Rage, not that it helps.
In the finale of Revolutionary Girl Utenathe previously unflappable Magnificent Bastard Akio Ohtori. When he sees that Utena has not only failed to give up, but also succeeded in what he thought was impossible and opened the Rose Gate, threatening the cornerstone of his illusionary power, he is immediately reduced to desperately begging her to stop what she is doing, and finally just wordlessly screaming in terror.