Anatolia Story has Nakia, who used to be a scared teenage girl whose father (the ruler of Babylon) ordered her to marry the king of Hattusa. Nakia was not happy about this, because Hattusa had invaded Babylon not so long ago, the marriage was blatantly using her as a political pawn, and the king was old enough to be her father. She goes through with it and ends up in a strange land, with a husband who has no interest in her at all. Lonely and angry, she ends up vowing to have a son and see to it that he becomes the next king, to ensure her bloodline continues to rule the land. By the time Yuri has arrived, Nakia occupies the second-most powerful position in the kingdom (which she achieved by poisoning Kail's mother) and is using every scheme she can think of to kill her stepsons and husband. As the series goes on, it's clear that she's willing to drive the entire land to ruin if it means getting what she wants, but she's completely and utterly alone the entire time, save for her right-hand man. Even her own son turns on her at the end, thanks to her insanity, and her ultimate fate is a Cruel Mercy: she's allowed to live in a nice villa, while knowing that she owes it to Yuri and Kail, who intend for her to witness how the Hitite Empire blossoms and flourishes without her in power.
In Animal Land there are five humans who can understand all animal "cries" (animals can't understand each other so predators have no problems killing prey, and prey can't work together to even things out a little, and every night these humans have to hear shrieks of pain and terror). One of them wants to use ancient technology to kill every living creature on the planet because when he killed his own abusive father he saw how peaceful and redemptive dying was. He's also the only one who knows about religion but didn't utilize it to create a death cult, which would have probably been much more effective than suddenly trying to kill everyone without their permission. The surprise second woobie just hates the fact that she, a clone of someone else, exist(s).
In Anti-Magic Academy: The 35th Test Platoon Kiseki Kusanagi's powers drive her mad sending her on two omnicidal rampages.
The Warriors aka the Titan Shifter Trio of Annie, Bertolt and Reiner from Attack on Titan fit the bill. Born in The Kingdom of Marley they were trained at a young age to be Warriors and kill the humans living within the Walls under the belief that they were "demons" who wanted to destroy the world. Only after destroying the Walls and letting in the Titans did they realise that the people they were send to kill were just that, people, which caused them emotional distress. Over the next five years they slowly integrated themselves to Wall life and, despite their best intentions, eventually came to care for several of the people that they were meant to kill. Once the deceptions are revealed they are shown to be wrecked with guilt torn between the bonds they created and the mission they need to complete. The stress of their deceptions eventually caused them to go insane and now all they desperately want is to complete their mission and go home.
By Chapter 123, Eren Yeager has become this in full. He lost his family to the Warriors' attack on his hometown, saw countless comrades die in subsequent counterattacks against the Titans, was driven nearly to suicide upon learning the horrific truths of the nature of his powers, finally realized that the rest of the world beyond the island is dead set on exterminating his people and won't even consider offering them a chance to negotiate for peace, lost the love and trust of his remaining friends when he put his plans to protect his home in action, and came within a hair's breadth of dying before he could activate the only deterrent powerful enough to stave off the world's armies. By this point, he is fed up with the vicious cycle of war, revenge, discrimination, suffering, and hopelessness and declares that he will use the Wall Titans to destroy all life beyond Paradis Island.
Guts, the Byronic Hero. He doesn't exactly want to destroy the world... but he is willing to walk a path of destruction to get to where he wants to be, and he doesn't care who gets in his way. Some say that Guts' quest to destroy the Godhand is suicidal and his seething hatred for the Apostles is just as horrific, and there might have been some truth to that before he got a call back to what was most important to him: protecting the woman that he loves, Casca. That's right. These two were unfortunate enough to have gone through the worst shit imaginable, and it will all end with both of them spending an eternity in hell thanks to their former friend making an epic FaceHeel Turn and sacrificing them and all of their other friends. The only way to spare him and Casca from this horrible fate in the smallest way possible? Kill every last one of The Legions of Hell by himself!
A very damaged soul is Rosine. Horribly mistreated by her cruel father, she mentally snapped from the abuse and accepted the Godhand's bargain, afterwards using her powers as an Apostle to lash out at the world. Even Guts who lives and breathes for the sake of revenge and sees Apostles (with good reason) as cockroaches, hesitates twice to finish her off, chastising himself that he will get himself killed if he continues. This means a lot coming from him.
Vincent from the Cowboy Bebopmovie, having gone self-destructively homicidal from psychosis and the inability to separate his hallucinations from reality after becoming an unwilling participant in a Supersoldier program that caused him to permanently hallucinate. His leitmotif "is it real?" just hammers it home.
Misa Amane counts, as well. Her parents were murdered and she was about to be killed by the same person that murdered her parents had it not been for Gelus. No wonder she's become so psycho and a huge Kira supporter. It's even more sad when she's interrogated by the police and was asking them to kill her.
Digimon Adventure 02: Yukio Oikawa. Growing up as a lonely boy in a unforgiving world, the only friend he ever had was Hiroki Hida, Cody Hida's father. During their youth, they became the very first humans ever to discover the Digital World, and they together promised that they would one day travel to it. Fate decided to be a mean bitch one day and killed off Hiroki during his line of duty as a police officer before it could happen, leaving Oikawa with no one else in the world but his promise. Depressed and lonely, he became a easy target for Myotismon's ghost to possess, who promised him that he would help him to get to the Digital World and fullfill his promise to Hiroki...at the expense of everything and everyone else.
Dragon Ball Super: Tagoma. Having been forced to be Frieza's practice dummy for four months, Tagoma was beaten within an inch of his life every single day for that time period purely so Frieza could find the best ways to effectively torture Goku before killing him; by the time of the invasion, Tagoma's sanity is shot to hell, and he's just as brutal and ruthless as Frieza himself. While Tagoma died with his convictions and what morality he had intact in Resurrection 'F', in Super, Frieza killed him in all except body. Then to add insult to injury his body is stolen by Captain Ginyu.
Vegeta. He had to be taken by Frieza, one of the universe's most evil characters from his father, King Vegeta, when he was a little boy in what was heavily implied to be a deal Frieza forced upon him. Then, Vegeta is forced to obey Frieza's commands or else he would murder his dad, and despite this, Frieza killed him anyways, and then committed genocide against his own people, and even afterwards he was treated by a slave by Frieza and his henchman, especially Frieza and Zarbon. When Goku learns of these details when Vegeta was dying from Frieza puncturing his heart with a death beam, even Goku took pity on him.
Broly is heavily implied to be this in the Eighth movie. The movie heavily implies that his destructive nature, even by Saiyan standards, as well as his overall insanity was the direct result of life-threatening factors from his birth, such as his nearly dying from a stab wound commissioned by King Vegeta simply because he feared his power level, and then having to witness Frieza destroy his home planet. Then his father places a slave crown on Broly and uses him to destroy several planets for his plan to get revenge on Vegeta for what his father attempted to do to Broly and himself.
D.Gray-Man: Alma Karma. Even though he has killed many Black Order scientists in the past, other in the present and wants to destroy the order, there isn't a single character who hates him. Actually they even feel sorry for him as the order is responsible for Forcing him and his loved one to fight and when they died they couldn't let him alone. They retrieved their brains and put them in new artificial body to force them to fight again. To be able master the empathetic weapon, Alma as a child was put under experiments so painful that his limbs fell off... . No wonder he snapped when he discovered the truth!
Lucy from Elfen Lied. Several characters think that it's her natural instinct to eradicate humanity, but given her past, her experiences alone would be enough to make her what she is. She truly believes that she is doing all those atrocities out of instinct, so if we look at the nurture aspect, we come to the conclusion that she Mind Raped herself (with a little help from nearly everyone around herand an inner voice / alternate personality that wants to eradicate all life) into believing that she was, in her own words, "born to wipe out mankind". Heartbreaking can't even begin to describe it.
Whatever spurred Black Mage Zeref to go and earn the reputation he has is a mystery, but he's so unbelievably miserable in the present that you just want to hug him. For the love of God, though, donothughim! He gets even more Woobie when his motivation for creating all the demons and dark artifacts was simply him trying to find a way to bring his brother back to life.He allows himself to believe that he can finally care about someone when he learns that Mavis suffers the same curse he does. Her kindness and desire to stand beside him so together, they could find a way to break the curse, or, if that weren't possible, cure each other's loneliness, is enough for him to fall in love with her. They kiss... but because Ankhseram is so intent on destroying any chance of him having happiness, his love for her is enough to break her curse and kill her, or at least, kill her body. It was this event that broke Zeref and turned him evil.
August fits this trope as well. August is part of the Alvarez Empire and Zeref's most loyal follower because he's his son. His mother Mavis was crystallized in Fairy Heart, and his father was God knows where. Precht abandoned him for years, until he met Zeref again and was recruited to help build Alvarez as is. Zeref never loved him because he never knew he existed, and because of his curse, August could never tell him he was his son. His death comes when he decides to sacrifice himself destroying Fairy Tail once and for all, but when he sees Mavis dying as well, he can't bring himself to do it and lets himself be consumed by his own power, despite knowing that Mavis never knew the truth either.
ToyMajin of the Fresh Pretty Cure! movie. He was tossed away by his previous human owner and he was filled so much bitter anger, he decided to steal away all toys, then use them to power himself, many of them filled with that same anger. When he captures Usapyon, Love's precious toy bunny doll, it breaks the Cure, making her think that she had the same hatred and drives her to try to make amends... only to find out she never hated her at all. Thanks to the children's love for their toys, Love's able to get ToyMajin to see the error of his ways and sees his true self... a teddy bear. Which she promptly gives to another kid who promises to take care of him.
Fruits Basket: After the full extent of the past is revealed, nobody can hold much hatred for Akito Sohma anymore. She has emotionally and physically abused the members of the Sohma family — stabbing Hattori in the eye when he asked for permission to marry, psychologically abusing Yuuki, injuring Rin to the point of needing the hospital — but she has been on the receiving end of nothing but the same type of abuse by her mother, Ren. Akito was raised under her thumb with the pathological fear of being abandoned, not respected, and unloved by everyone, leading to her doing anything to keep people around.
Scar from Fullmetal Alchemist is one of the few survivors of a brutal genocide which killed almost all his loved ones. As revenge against the government who massacred his people, he becomes a Serial Killer who exclusively targets state alchemists. Fortunately, in both manga and both animes, he gets better.
At the end of Fushigi Yuugi, Tamahome unintentionally has a Psychic Link to Nakago's mind revealing his past when he was a young boy, his entire tribe was wiped out, he witnessed his mother being gang-raped, and accidentally killed both his mother and her rapists with his awakened power, only to be sent to the Emperor of Kutou, who raped him repeatedly. As a result, he wants revenge on existence itself for giving him such a horrible life.
Tsubaki of Future Diary was imprisoned as a sex slave by a cult her whole life before receiving her Diary, and now participates in the Diary game with the stated goal of destroying the world.
Yuno wants to keep the universe in an eternal time loop, forever replaying the Diary game, as this is the only way she believes she can stay with Yukiteru. She wants this so desperately because Yuki is probably one of the only kind people in her life, and her sole reason for living.
Brandon Heat, or, more accurately, Beyond the Grave, from Gungrave. A nigh-unkillable, unstoppable killing machine capable of destroying armies of super-powered zombies single-handedly with more firepower than some developed nations, by the time he becomes Beyond the Grave, he has forsaken the love of his life because he thought that she deserved better than to be with a ruthless hitman, watched his boss, who was the father he never had, marry her, and been killed by his best friend (he got better) and resurrected by the daughter of his former lover to protect her. He does this by killing all of his friends, including his best friend and his mentor. And, in the finale, himself.
Haruhi Suzumiya: After going through nearly 15 and a half thousand of the same 2 weeks, Yuki gains emotions and becomes this. Except that she doesn't destroy the world. She steals Haruhi's powers and RetCons reality for 1 year, according to the novels, and 3 years and 5 months, according to The Movie. And she succeeds. And she's stopped by the protagonists. And, for a point in time, there's 4 Kyons and 3 Mikurus.
Heavy Object: Nyarlathotep, from Volume 10, is a former member of the Capitalist Enterprise intelligence group Outer Gods, a cabal of spies who treated each other like family. As a spy, he has gotten multiple plastic surgeries, and has faked his death numerous times. Once their leader/former friend, Azathoth, retired to become a member of the 7th Cores ruling the Capitalist Corporation, Nyarlathotep decided become a family man residing in the peaceful Soberania District. Nothing can go wrong. Well, that is until his wife and son are killed when Azathoth destroys his town. As a result, Nyarlathotep no longer cared about anything except avenging his family. Starting psychological warfare between various factions in order to start the Gigant Hustler, an event showcasing Objects fighting each other. During the Hustler, Nyarlathotep infiltrated the battlefield and sabotaged the Baby Magnum to lure Azathoth to the event. Once the event is canceled, Nyarlahotep impersonates Azathoth's driver and takes him to the remains of the Soberania District, showing him what he's done to his once great city and family before killing him. Once this was discovered, Nyarlathotep is subjected to a farcical military trial by the Legitimacy Kingdom in order to avert a war that almost started between every faction. He then killed the assassin sent to silence him in his cell and faked his death once again, before departing to elsewhere.
Yuca from Immortal Rain doesn't know how old he is. All he knows is that, whenever he dies, he's reborn long after everyone he knew before died, while still retaining the memories of each of his previous lives. Over and over again, throughout what seems to be the course of human history. By the point we meet him, he wants to wipe out all humanity just so he can finally die and be able to stay dead.
Prince Djeser from Im Great Priest Imhotep started as the Wide-Eyed Idealist heir to Pharaoh, dreaming to usher a new Golden Age for Egypt by reuniting the royal family with the priesthood, helped by his best friend Imhotep. What he didn't know was the fact he was born to be a Human Sacrifice, his soul destined to suffer in Hell for eternity to prevent a Zombie Apocalypse, and everyone else knew it. When Imhotep tries to find a way to save him, the other priests lock him away before casting the ritual and ripping out Djeser's heart, right after using Imhotep's appearance to cruelly mock Djeser's dream. When the ritual goes wrong because of Imhotep's intervention, The Power of Hate transforms Djeser into a vengeful zombie responsible for creating many demons and evil gods, hell-bent on destroying the world for his suffering and bitterly regretting his friendship with Imhotep. Ouch doesn't even start to cover it.
Alma Jinnai from Jewelpet Twinkle. Born as a twin from Fealina, one of Jewelland's greatest magic users who "died" trying to reseal Battest, she becomes the only one to possess magical power. In fact, her magical power is much higher than average, necessitating her to live separately in Jewelland away from her brother Yuuma, and turning her into lonesome girl always avoiding contact with others. Years of living in solitude with absolutely no friend other than her self made Jewelpet, Diana, causes her to be rather shortsighted, her only aim being to revive Fealina in any way necessary, even by utilizing dark magic and Battest, despite the fact that doing so will bring disaster to Jewelland.
The Lucifer and Biscuit Hammer: Yuuhi, with a Freudian Excuse to match: his father, a detective, was killed by his colleague. After the funeral, his mom simply left, and his grandfather beat into him the idea "Make no enemies - they'll stab you in the front; make no friends - they'll stab you in the back." Sami's reasoning is that she wants to own the world by destroying it so that it doesn't go on without her when she dies.
Hayate Yagami became one, though it required a massive Break the Cutie moment created by other parties to push her past the "the-world-has-hurt-me-so-much-it-deserves-to-die" breaking point, and when she regained her senses, she chastised her Artifact of Doom for thinking that that's what she really wanted and put a stop to things.
The Book of Darkness is a woobie because she's a destroyer of worlds. Her life cycle has three phases: charging up in dormancy, gaining full awareness and control for a few minutes, and then dishing out an Earth-Shattering Kaboom, which returns her to stage one. Prior to her current appearance, she has been forced to serve a cruel master who abused her children. Bonus points for the fact that there is nothing that can be done to stop the cycle.
And Admiral Gil Graham in A's, who set the whole thing up in order to seal the Book of Darkness when it awoke. That Hayate would be collateral damage was unfortunate but unavoidable in his mind. Nobody judges him too harshly for this, because, honestly, no one else had come up with a better plan for stopping the Book.
The Mazinger saga has two of these:
Dr. Hell in the original Mazinger Z manga. Everyone (including his parents. In particular his mother 'repeatedly' complained she never wanted having him, and hit him for any reason) abused him and mistreated him during his childhood and teenhood years until his mind finally snapped out, and he decided one day he would purge the world of idiots, and everybody would have to bow down to him. He was still dreaming of doing just that several decades later when he finally found the means to do so as exploring the ruins of an ancient, lost civilization.
In the Darker and Edgier reboot Shin Mazinger Zero, Koji Kabuto himself became this as he literally lost everything in the first chapters. To wit: his father was murdered, his girlfriend was raped AND killed, he killed the culprit (his grandfather, of all people), lost an arm... and then not only he became this trope, but he and Mazinger ended up literally destroying Earth. And for worse, a Robot Girl named Minerva-X witnessed everything and couldn't do anything to help but pressing a Reset Button. Then he found himself back to his supposedly normal world as a result of said Reset Button use, unable to properly remember what happened, until Minerva showed up as a supposed New Transfer Student, determined to help him avert this trope so the planet won't be destroyed again.
Tima of Osamu Tezuka's Metropolis (2001). After getting shot and realizing that she's a robot, she takes control of immeasurably powerful technology and orders the extinction of humanity.
Lord Fezarl Ezelcant, the Big Bad of Mobile Suit Gundam Age, is a married man and was a father. However, the death of his son convinced him that it was high time to root out the weak by waging a war that would eliminate them and create a paradise populated only by the most righteous of humans. Thus began the UE's attacks on Earth Federation Colonies. In the third generation,note The show's hook was that it would not follow an overall short war and one group of people as per Gundam tradition, but take place over three generations and nearly a century. fate really twists the knife by having him encounter a young boy who greatly resembles his son... Who just so happens to be a Federation pilot and the grandson of Flit Asuno, the main hero of the first generation and the biggest Vagan-hater alive. Ezelcant's son, in his last moments, said that he'd like to be reborn on Earth along with them. Ezelcant is convinced that his son got half his wish.
Rau Le Creuset from Mobile Suit Gundam SEED. He's a dying man at 28 years old, born with telomeres of the thirty-something Al Da Flaga, his genetic "father". He's in constant pain that can only be subdued by drug dosages that double twice over the course of the series. His dealings with people, hatred of his flawed body and the people who ensured that he was born that way, his emotional pain over his Parental Abandonment, and being a clone and thus seeing himself with no "identity" of his own eventually became a bitterness towards humanity in general. He descends into full Straw Nihilist territory, convinced that humans only inflict pain and suffering on others, not least of all himself. Aware that his own existence cannot be considered human and is more or less the personification of mankind's sins, he took it upon himself to be the Judge, Jury, and Executioner of humanity, and in a very literal bid to make the pain stop, he tried to Kill All Humans, and nearly succeeded. By the time he sentenced all of humanity to annihilation, he was more or less reveling in the fact that his view was "vindicated" by the actions of Muruta Azrael, who had just tried to wipe out all Coordinators with a nuclear missile array, and Patrick Zala, who was preparing to annihilate all life on earth with GENESIS. A life or two was meaningless at this point.
Stella — she stomps through city and wilderness alike in a giant robot, slaughtering innocent bystanders by the thousands because she's driven by a childlike, irrational terror of death, and has been told that if she doesn't fight, scary things will kill her and everyone she cares about. The fact that she's just being used by Neo and Djibril, who are deliberately playing on her fear and pain, makes this all the sadder.
Shinn Asuka, the initial protagonist, is even worse. Like his Mobile Suit Zeta Gundam counterpart Kamille Bidan, Shinn is a bundle of emotions that can only really get loose through Mobile Suit combat. However, unlike Kamille, who had people like Amuro, Quattro and Bright to keep his head on straight, Shinn is instead manipulated by Chairman Gilbert Durandal and his own teammate Rey Za Burrel, turning him into The Berserker armed with a senses-enhancing Super Mode and a hyper-advanced Gundam, all in the name of protecting those he cares for and preventing past tragedies, not realizing he's making the same ones.
Enchu in Muhyo and Roji, as it's revealed late in the series that the real reason he turned to evil was not out of hatred for Muhyo, but a desire for release from his pain. Some of his accomplices, including Rio and the Cortlaw Siblings are spurred on by the loss of loved ones, including the desire to return them from the dead.
Hiroko "Hiro-chan" Kaizuka from Narutaru is an intelligent, modest young girl who is broken by abuse from both unbelievably sadistic bulliesand overly demanding, repressive parents. Eventually, she, along with her Shadow Dragon, Oni, attempts to make everything she doesn't like disappear...by way of going on a horrific, murderous rampage.
Nagato which was witnessing his parents being killed when he was still a child. Though he did get revenge by activating the Rinnegan and killing the two shinobi who were mistaken as assassins. Nagato became an orphan, finding companionship from Yahiko and Konan, and was taken in by one of the Legendary Sannin, Jiraiya, who took him and his friends in and taught them the ninja arts so that they could protect themselves and each other. This all went downhill as the group was locked into a Sadistic Choice that resulted in Yahiko's death, following which Nagato slaughtered a good number of the opposing force at the cost of his health. Nagato then obsessed with finding a method to establish absolute peace: whatever brought him into the Big Bad's clutches, it led to him demolishing a village full of people and leading a one-man (well, six or seven) assault against Konoha.
The biggest example in the series is Obito Uchiha aka Tobi. Since childhood, he was an orphan which not knew who his parents were, being outcast in his own clan and forced hide behind the act of a happy-go-lucky idiot to escape his loneliness and pain as a child. However, once he was crippled and mutilated in a cave in and later witnessed the girl he loved and acted kindly to him being killed in a twisted war plot freehand of his best friend who promised to protect her at any cost, he went completely insane discarding the world as a fake that he had to replace with the Moon Eye Plan. In the span of a few months, he went from saying that those who betray their comrades are worse than trash to holding his sensei's newborn son hostage, killing his sensei and his sensei's wife, nearly annihilating his entire village and when his sensei's dying act thwarted his efforts, he plotted the extermination of his own clan. Nagato unleashed his woobie-induced rage on his enemies; Tobi unleashed it on his friends!
Neon Genesis Evangelion: Shinji Ikari turns into this during End Of Evangelion. After spending the entire series watching/hearing most of the friends he made die in the most horrifying ways, then having to accept that maybe he would never get a normal relationship with his father, then having to decide to continue piloting the EVA for the world's sake, then having to kill someone who showed love for him, then have to see the girl that he loved had been chopped into pieces maybe it was a mistake to let him decide what will happen to mankind.
Kanto from SoilNew Town has had a rough life. His dentist drugged and raped him as a child which caused him to feel so ashamed and, well, soiled that he cut himself; it got worse when the dentist reconnected with him in high school and, as proof of his twisted "pure" love, gave him the video of his assault. The shame intensified to the point where he couldn't stand to watch cats in heat and tried to burn down the resident homeless crazy cat lady's shelter (fortunately, he didn't succed). Things seemed to get a little better when he met a nice girl, but just as he was about to have his first consensual sexual encounter, she disappeared from between his legs. No wonder he wants to destroy the world by enlisting the dentist's roughly three dozen unwitting current victims plus a victim by proxy (her rapists were also the dentist's victims) to cause enough anomalies to break reality.
The protagonist, Ueki Kaito, was dragged to a new world against his will by Princess Alesia ostensibly to save her people from the Demon Lord. He spends three years doing just that, training and adventuring with little if any rest until he succeeds. Once he succeeds, the suffering truly begins. The companions picked out for him, including the princess herself, all turn on him. For an entire year, he is hunted like an animal, framed for every crime imaginable, and every single time someone reached out to him, offering aid and shelter, the person in question would happily sell him out the moment his guard was down. The princess herself even corners him once, purely to taunt him concerning the fact that the 200 hundred people physically closest to him at the time he was summoned were slain, and five close relatives died horribly, just from the summoning alone, and it would take a similar sacrifice to even think of going back. At the prologue, the so-called companions all caught up to him and repeatedly stabbed him in the chest, looking upon him with derision for the fact that it's taking so long to kill him, patting themselves on the back "for slaying evil" as he dies, swearing vengeance. Then he wakes up, four years in the past, right back in the summoning chamber, face to face with the very Princess Alesia who summoned him. Not letting himself become her pawn this time, he sets off on the path of vengeance.
Originally, Millanis (Minnalis) was a sweet little girl, taught an illusion spell by her mother to hide her beast-man features from the world, not comprehending the concept of racism. At the age of seven years old, while she was searching for food in the forest with her best friend, Lucia, due to early winter, the two of them chanced upon an Ice Goblin. Lucia panics, screams, and freezes in terror drawing the Ice Goblin's attention, endangering the both of them. Rather than fleeing and leaving her friend to die, or worse, Millanis uses her full strength to fight and drive off the Ice Goblin, revealing her beast-man traits. Initially grateful, Lucia promises to keep the beast-man heritage a secret. Millanis learns, to her horror, that Lucia did not keep her word, as the entire village was up in arms, dragging her out of her home, demanding she should reveal herself as a beast-man, and demanding her mother reveal herself too, with Lucia loudly proclaiming that Millanis forced her into silence, by threats of violence, then smirking and taunting Lucia hiding behind the backs of the mob of angry villagers. Not getting a chance to defend themselves, Millanis and her mother were stoned, beaten, driven out of the village and sold into slavery, where the slave merchant and their fellow slaves beat and abused them horribly for ten years, Millanis's mother dying in the process. When Ueki Kaito found her in the slave tent, she was on the verge of starving to death and being thrown away. She wasted no time in carrying out her vengeance on the merchant and her fellow slaves the moment Kaito gave her the chance.
Originally a sweet, blonde, happy little girl born of an illicit union between her mother and a duke, Shuria grows up in a remote village after the duke's legitimate wife throws her mother, expecting her, out of the family home. She takes up adventuring, and is quite skilled at it, due to her peerless magical talent. One day, her younger half-sister, Selena becomes ill with a fatal disease, but no matter how hard she works, she can't afford an elixir, the only known cure. Her older half-sister, Yumis turns up at the village, promising to provide the cure, if she'll turn over her superior magical talent. Having no other valid option, she agrees and spends three years locked up in a room, unable to leave, but sitting in the lap of luxury, provided with audio recordings proving that her friends and family are safe and sound. Upon the day the ritual to extract her magic is complete, and she's allowed to leave, Yumis takes her around town for a farewell "date." At the end of the date, she begins growing suspicious as Yumis doesn't take her to her home village, but instead a run-down shack. It is at this point that Yumis stops pretending and adopts her true personality, revealing that the entire village was fed to a demon to power the ritual to transfer her magic talent, her mother and younger sister greet her as undead corpses, the audiotapes were faked, and the same demon who killed her village was promised her own soul. She struggles valiantly in impotent rage, promising vengeance. Kaito rescues her, promises her the chance for revenge, and she happily takes it.
The eponymous Big Bad from Noein is this. It is revealed that he is a possible future of the male lead, who, upon losing his true love in a car crash, started desperately searching the time streams for a way to save her. Unfortunately, he found the multiverse to be full of pain and suffering, and decided to destroy everything and start it over from scratch.
Pokémon: The First Movie: Mewtwo's motivations for wanting to conquer the planet in the first movie become a lot more understandable when one remembers his childhood, when his only friend disappeared without explaining why he was there and, in the height of his angst, his memories were forcibly erased. Even after his birth, he was taken advantage of by Giovanni until he'd had enough.
Moe/Molly from the third movie is a lonely little girl whose mother is long gone and her father is sucked into the Unown dimension. As she cracks under the pressure, the Unown try to make little Molly's wishes come true and transform the mansion into a crystal palace, finally creating an Entei as Molly's father. Said Entei happens to be loyal to Molly to an insane level, kidnapping Ash's mother Delia to make her Molly's mom. And then the Unown's powers start going haywire...
This was actually invoked by Homura in the third timeline. The two of them have beaten Walpurgis Night, but their Soul Gems are almost completely darkened. Homura's resigned herself to the two becoming witches and destroying the world. Madokadisagrees.
To some extent, Witches in general qualify. A Witch is made when a magical girl lets The Corruption take over her soul gem, transforming it into a grief seed. This usually happens when they cross the Despair Event Horizon. Now remember how many times characters are put into danger or outright killed because of Witches.
Puella Magi Madoka Magica the Movie: Rebellion: Homura finally succumbs to this. We see that she resented Madoka's aforementioned sacrifice, and her Witch form finally emerges. When Goddess!Madoka comes to take her to "heaven", Homura fully becomes this: she then steals her powers and returns Madoka to human form, at the cost of herself becoming the Satanic Archetype to Madoka's Messianic Archetype and eventually having to become her enemy. She then places the entire universe under her control, and maintains the illusion by wiping everyone's memories. And yet...she still feels grief-stricken over the prospect of possibly becoming the series' Final Boss, and is ultimately trapped in a Self-Inflicted Hell.
Despite being destined to destroy everything, Ashura's true self in RG Veda might as well be one of these. His whole race was eradicated, his own mother disowned him and tried to kill him when he was just a few hours old, whenever people see him, it's either to declare him a "cursed child" and try to kill him or be nice to him and die themselves to protect him from his pursuers. Even the prophesy supports this: the prophecy says that "the red lotus flame would destroy all evil"; Ashura has power over flames and the fact that he would destroy everything he considers evil heavily implies that, despite his usual idealistic self, Ashura holds great hatred for the world that has been so cruel and unfair to him just for being born as an Ashura and really wants to see it burn. Only his love towards Yasha, the only one who loved him to the point of sacrificing a lot for him, was stronger than his hatred and omnicidal nature.
Invoked by Wiseman, who Mind Rapes and forces a Plot-Relevant Age-Up on Chibi-Usa to make her believe she has been abandoned by everyone who loved her, thus making her The Dragon and his most loyal follower — the Black Lady. It works for a while, but she's freed from this in the end by Sailor Moon and reverts to her original self.
People under the influence of the Kisenian Flower in Sailor Moon become this. The Kisenian Flower specifically targets people with weak hearts, feeds off their negative energy, then destroys the planet they reside on and waits on the fragments until they find another willing host.
Hotaru. Woobie? Easily the biggest in the series. Capable of destroying the planet and everyone on it? You bet.
Homura from Saiyuki: sure, he wants to bring an end to everything in existance, but he's so sweet and vulnerable, and so many undeservedly terrible things have happened to him. His two henchmen fit this trope, too!
Goku. If it weren't for the merciful goddess replacing his broken power limiter when he did he would have killed Rikudo for almost killing Sanzo before Sanzo ever had a chance and before this he goes from adorable little boy to killing machine once his power limiter breaks and he kills hundreds of people upon witnessing his best friend (And only one his age) commit suicide so close that his blood get on him, all so that way he would not be forced to kill Goku and used as a pawn in his "father's" plans anymore. Then later when it breaks again from his overwhelming fear of being alone again and the monks chasing him in the temple just days after Sanzo saved him from the cave he was trapped in for 500 years.
Valgaav from The Slayers TRY. A tormented half-demon dragon who believes that all cosmic forces in his world are caught in an endless, senseless war that only causes suffering, and wants to erase everything from existence to end this.
Crona of Soul Eater has the 'destroy everything' part, by way of their reasoning that everything that they fears/threatens them should be destroyed (for much of the series, they understand no other way of 'dealing' with it). Given that Medusa did and still does possibly intend to turn Crona into an Eldritch Abomination in the style of madness incarnate Asura, they could feasibly go all the way on this one. Until Our Heroes inevitably defeat them.
In the manga, Crona is the Big Bad despite being a favorite character of the audience and cast. Crona ultimately takes all that potentially destructive power of becoming a Humanoid Abomination like Asura, and consciously uses it to imprison Asura on the moon, even at the price of Crona's own freedom.
Choji Suitengu, the Big Bad of Speed Grapher. His ultimate goal is to die after destroying the corrupted culture of greed that Japan had become, as they forced him and his sister into a living hell.
Mantid from Spider Riders — he loses the love of his life in war; it's implied that he lost many friends the same way, and it may be that he lost his spider partner as well, which makes sense because we never get to see it. With all that, it's no wonder the guy went off the deep end.
In Tokyo Ghoul, there are several of these running around.
The One-Eyed Owl aka Eto, the only known case of a natural Half-Human Hybrid and a Living MacGuffin. The product of Star-Crossed Lovers, her Ghoul father was forced by his superiors to kill her human mother shortly after her birth. In order to protect her from his superiors, Yoshimura was forced to abandon his infant daughter in the 24th Ward. Forced to kill and cannibalize other Ghouls to survive, she mutated into a Kakuja at a young age and began launching attacks against the CCG. Her father blames himself for his beloved daughter growing to hate the world, and pleads with Kaneki to find some way to save her from herself. As Sasaki, he explains that her novels reveal an author that has suffered greatly, completely giving up on being loved and unable to trust people. She frequently muses on the subject of love, while making it clear she believes it is merely something that destroys or controls people. Suffice to say, while the greatest threat in the series, the Owl is an enormous ball of anger and pain that wants to destroy everything as a result of a lifetime of suffering and loneliness.
In the sequel, Seidou Takizawa has become one. Even while slaughtering his way through Investigators, and torturing Sasaki while giving him a Breaking Speech......it's painfully obvious that his actions are a result of the physical and psychological torture he's endured for years on end.
Trigun features Legato Bluesummers, The Dragon to Millions Knives. He's got a sympathetic backstory as a nameless sex slave and, like Knives, has let his own pain drive him into becoming an Omnicidal Maniac. Problem is, he's an utter, sadistic psycho with a murder habit, who likes to torture the lead, reducing any sympathy factor for him both in-universe and out.
Formerly peace-loving anti-war Amnesiac Hero Nana:IT IS TIME TO MAKE THE WORLD PAY FOR ALL THE SUFFERING THEY'VE PUT US THROUGH.
Video Girl Mai becomes this in Video Girl Ai, after ending up as a Sex Slave to a boy without a pure heart and going mad as a result.
Darcia from Wolf's Rain, who, after the loss of his lover, Hamona, turns insane and decides to ruin the paradise the protagonists are trying to create. In a sense, he doesn't want to destroy the current world, as the Earth is dying anyway, but prevent the next.
Yami AKA Atem becomes this for a bit in the Doma saga after he loses Yugi - especially during his duel with Haga. Oh, silly Haga, didn't you know that pretending to destroy the soul of a highly protective and emotionally unstable (and once-Axe-Crazy) ancient spirit's partner was just asking for a one-way ticket down extreme-pain-and-death lane?
Thief King Bakura might count, given that he became what he was because he survived and witnessed the gruesome killing of all the people in his village. Granted, they seemed to be a village of thieves, but still, he was an innocent child before this happened.
Malik Ishtar became cynical and evil from his father's abuse of him including a painful skin carving covering his whole back.
Pegasus became this after losing his wife and having his left eye forcibly replaced with a Millennium Item.
Diva/Aigami from the "Dark Side of Dimensions" movie continuity certainly qualifies; literately having the ability to rearrange other dimensions and kill people in them. As a child, he and his sister lived with an abusive and neglectful man in Egypt, Until Shadi adopted them and cared for them alongside a bunch of other kids. They were taught all about the Pharaoh and told that when he returned to this world and left again for good, they would all be able to enter a portal to a better world. One day, Ryo Bakura's father found the crypt and wanted to buy the millennium ring. Upon being tested, Yami Bakura killed him. When Bakura ran to his father from his hiding place, the spirit of the ring bonded to him and possessed him. Diva was given some of Shadi's powers and his magic cube before he saw his mentor killed in front of him, along with all the other kids, leaving him and his sister as the sole survivors. After this, he developed quite the hate complex; wanting to not only kill Bakura, but Yugi Mouto and Seto Kaiba as well, as he blames the pharaoh and priest Seto, who the two are reincarnations of, for the existence of the millennium items.
Yu-Gi-Oh! GX: Judai goes insane with grief and awakens his Super-Powered Evil Side after watching his friends be sacrificed before his eyes. Trapped within his own mind, his other self goes on a murderous rampage in the pursuit of power so as not to be hurt again.
Izayoi Aki for episodes 40 and 41. After watching her friend and mentor Divine plunge to his horrifying death, while the only place she'd ever really felt at home in collapses in flames around her, she wakes up from a coma where she relived every single horrible moment of her life all at once to the face of Yusei, who she already feels conflicted about - and her parents, of all people. Destroying the world from there though, yes, seems like Disproportionate Retribution, but is not that much of a stretch.
Aporia, Z-one, Antinomy, and Paradox, especially Aporia, too. The only survivors of a Bad Future, they only seek to Set Right What Once Went Wrong ...at the expense of Neo Domino city and it's inhabitants.
Shinobu Sensui of Yu Yu Hakusho began as a heroic spirit detective, but had a mental breakdown after discovering humans torturing demons, throwing his life's work of protecting humans into question — one that isn't helped by his subscription to Black-and-White Morality. His mind, now fractured into seven split personalities, embarked on a plan to destroy humanity as a way of ending the confusion and guilt, along with a Suicidal Cosmic Temper Tantrum over his terminal illness.