Haruyuki's fatal flaw is his lack of self-esteem. Not only does this frequently hold him back in battle, it also means that he initially doubts that Kuroyukihime would be interested in him, leading to some tension between them.
Takumu also suffers from poor self-esteem, but it's a bit different in his case since he's prone to punishing himself for his mistakes and wallowing in his guilt.
Parodied in Air Gear when Spitfire points out that Ikki has a crippling weakness, that he sucks at using AT. Ringo has to admit he's not wrong.
Akame ga Kill!: The unnamed Emperor's blind faith in the Obviously Evil Prime Minister Honest makes it easy for the latter to manipulate him, leading him to run the empire he's supposed to rule to the ground and allowing corrupt nobles to get away with their atrocities. It all leads to the breaking point when Honest uses him to power the Ultimate Teigu: Shikoutazer and mentally brainwashes him into going on a destructive rampage, killing and endangering the people he's supposed to protect. By the time he finally realizes Honest's true nature, it's already too late, and he's ultimately sentenced to death for his actions.
In Attack on Titan, Eren is very emotionally driven (especially by histemper) and can be reckless at times, which tend to him making decisions that end up having negative consequences for himself and others. Such as trying to avenge Thomas's death, resulting in most of his team's deaths and himself being eaten. His other flaw is his rigid view of morality, to the point he doesn't see the middle ground. Case in point, his reaction to villains expressing guilt, only enrages Eren even further as he believes that they shouldn't feel remorse. His vengeful nature and rigid morality eventually lead him to concluding all humanity not on Paradis is the problem, and attempting to commit genocide.
Mikasa's protectiveness over Eren had her prioritizing his safety over everything else, including her own life, which clouded her judgment and made her less efficient as a soldier. When she thinks Eren died in Trost and again when the Female Titan captured Eren, she became recklessly suicidal, and at one point, it led to Levi being injured to save her.
Grisha Yeager, Eren's father, may also take the cake of this trope as well. His naivete, foolishness, and inability to see the consequences of his actions unless it's presented to him have caused a downfall of him and everyone he cares about. First when he and Faye went out of liberal to see the blimp land until they were caught by officials leading her sister to her demise by a sergeant. Second was distancing himself from his first son Zeke and forcing nationalism into his life trying desperately to have him be chosen to be a shifter for the restoration's plan and never sparing a moment for how he feels and never seeing him and understanding him as the boy he was to the point he turns on him and his wife Dina, leading them and the rest of the restorations to hours to days of torture for information and being sentenced to paradi for treason as Pure Titans
In Bakuman。, Nanamine's fatal flaw is his inability to empathize with others. Not only does it lead him to twice attempt to rise to the top of Jump by using consultants, all the while viewing people as expendable, but it also means he is unable to write characters with "heart", in spite of his talent as an artist.
Banana Fish brings this up in regards to Ash's devotion to protecting Eiji, and how it endangers both of them. This is exploited by Blanca, a professional assassin hired by Golzine and Lee Yut Lung.
Bofuri: I Don't Want to Get Hurt, so I'll Max Out My Defense.: Mii's severe flaw is that, while her skills are deadly, she burns through MP/MP Potions like no one's business. Once she runs out of both MP/MP Potions, she's basically reduced to her basic attacks, something another person can utilize to their advantage via a battle of attrition and her Flame Prison can be easily undone, as it requires a very lengthy amount of time to cast, and if Maple and her comrades were slightly smarter in tactics and so forth, they wouldn't have fallen for both it and prevented Shin from running off with their goal point collection.
Aizen's god-complex and arrogance have him believe that he was above everyone else leading him to discard strategy and cunningness (what had previously allowed him to outsmart and outplay his enemies). He relied too much on his unnatural power upgrades and became Drunk with Power, which would lead to his defeat at the hands of both Ichigo and Urahara.
Shinji's distrust of Aizen meant that it was easy for Aizen to get away with his scheming because, as Aizen himself points out, Shinji never got to know Aizen as a person so when Aizen sent an imposter disguised as him to carry out his vice-captain duties, Shinji never noticed the imposter was a fake.
Hinamori's infatuation with Aizen meant he was able to play her like a fiddle throughout the Soul Society arc. After he's supposedly found dead, she flies into a rage and tries to attack Ichimaru (his supposed murderer, but actually his accomplice), and ends up fighting with her friend Kira when he defends his captain. After reading a letter that Aizen wrote and arranged to have delivered to her in advance of his death, she fights and tries to kill her Childhood Friend Hitsugaya. She is so deep in denial that even after Aizen almost kills her, she's convinced that Ichimaru is somehow controlling Aizen.
Ichigo believes that his Chronic Hero Syndrome is what directly lead to his mother's death — he saw a young girl about to fall into the river and ran to help her, ignoring his mother screaming at him to come back, only for the girl to be a lure from a hollow. His mother ran in to save Ichigo and was killed, which he blames himself for. Later, it's revealed Masaki could have killed the Hollow easily... had she not been depowered at that exact moment.
Neliel's condescending underestimation of Nnoitra comes back to bite her in the ass twice — first, she continually follows him around on missions and rubs it in his face that she has a higher rank, never finishing him off in their fights because he is of a lower rank than her and thus poses no threat, which to Nnoitra was disgracing him as a warrior. Nel is therefore utterly unprepared when Nnoitra teams up with Szayel, nearly kills her Fraccion, and then cracks her mask, crippling her by turning her into a child and throwing her out of Las Noches to die. Then, when they meet again in the present, Nnoitra points out during their fight that the Espada have grown much stronger in her absence and Nel refusing to kill Nnoitra despite the threat he poses means that when she unexpectedly returns back to her kid form, he promptly curbstomps her (once her powers go away), then starts torturing Ichigo in front of Orihime before Zaraki shows up and intervenes.
Hiyori'sHot-Blooded, Leeroy Jenkins tendencies really backfire on her several times in the series — when she continuously goads and provokes Ichigo as his Superpowered Evil Side starts taking over him, she gets slammed into the wall and nearly gets choked to death for her troubles and it's only the other seven Visoreds pinning him down that saves her. Later on, during the battle over Fake Karakura town, she ignores Shinji's warnings and tries to attack Aizen head-on and Gin responds by bisecting her. If it wasn't for Hachi and Orihime, she'd be dead, no question.
Yuu Koito, one half of the main couple, Thinks Like a Romance Novel and has unrealistic expectations when it comes to love. Because of this, when Touko seemingly rejects her, Yuu concludes that because she didn't break down in tears as Akari did, she never truly loved Touko. It takes her a few chapters to realize that she's mistaken.
Touko's fatal flaw is her poor self-esteem. She wants to discard her past self- an untalented girl with few friends- and become a copy of her sister. Unfortunately, the way she views that process means that when she achieves that goal and becomes as successful as her sister had been, she believes that her friends and admirers adore the facsimile of her sister, not her as a person, even when this is not the case.
Sayaka's fatal flaw is her passivity when it comes to Touko, and her unwillingness to challenge the status quo. Since she's afraid of losing the friendship that she and Touko share, she chooses to silently support her, not letting on that she knows about Touko's vulnerability or that her quest to become like her sister is doomed to failure, let alone that she's in love with Touko. As a result of this, by the time Sayaka confesses to Touko, Touko has already fallen in love with Yuu, and so rejects Sayaka.
According to Shura of Blue Exorcist, Yukio could be exploited by demons because he keeps his emotions bottled up unlike his more hot-headed brother Rin. Likewise, Rin has trouble controlling his flames because he's afraid of them.
A Certain Scientific Railgun: The main character, Misaka Mikoto, as her title nickname "railgun" suggests, is a straightforward person who resolves her problem by bumping into them head first (helped by the fact that she is the 3rd ranked level 5, one of the most powerful people in Academic City. But when faced with the level 6 shift project, an experiment which resulted in the deaths of 20000 of her clones so the first-ranked level 5, Accelerator, could raise his level, a problem she can't end by beating the responsible parties, she falls into a severe Heroic BSoD, aggravated by the fact that she refuses to ask for help.
In Chrono Crusade, Chrono's demonic instincts and need to protect others (particularly Rosette) sometimes combine to give him a very, very dangerous temper. Since Chrono's powers drain Rosette's lifespan due to their contract, it's dangerous not just to him, but to Rosette herself. In fact, in the manga, this trope is taken literally, when Aion provokes Chrono into unsealing his powers himself and come at him with everything he's got. Several people are killed in the battle, and it drains so much of Rosette's life that the next time she unseals the watch, she dies.
Lelouch does things without considering their negative consequences, keeps too many secrets, and doesn't trust people.
Suzaku has a large lack of self-worth and is too much of an idealist for his own good. Suzaku is unable to see that the people he sucks up to due to his lack of self-worth and desperate desire to be a Britannian are everything that he does not want and he is doing everything he claims he is against on a daily basis.
Shirley's love towards Lelouch gets her killed when she confronts Rolo. Even though she doesn't remember Rolo, she trusts him because Lelouch seems to trust him.
Prince Schneizel's detachment makes him ignorant of the situation and makes him vulnerable to be controlled in the end by Lelouch. Yet Schneizel is hypocritical and thinking just in the box. As Lelouch ever stated it to him. Additioanlly, there's his absolute refusal to lose, which causes him to try and do a sophisticatedRage Quit rather than admit defeat.
Ange's biggest flaws are her stubbornness and trust issues, which make her unable to see when she's in over her head. A prime example is in "Salia's Gloom" when she tries to fight a new type of DRAGON alone, while sick. She only makes it alive because, for once, she follows Salia's orders and lives to fight another day. Another of heris frequently running her mouth, which gets her slapped on more than one occasion. This is perhaps best shown when she starts going on about how she considers Libertus to be a joke... only to discover that she just insulted Tusk's parents, who died for the very mission she just called "pathetic". Although to her credit, she at least feels guilty enough about this to apologise later (which, for her, is a big deal).
Jill's anger towards Embryo for everything that he did to her in the first Libertus turned her into a bitter woman who won't stop at anything to get her revenge, no matter who or what she has to sacrifice to do so, viewing her subordinates as tools for her goal. This attitude, coupled with everyone learning about her hidden past leads to all her subordinates turning on her, and gets her killed by Embryo in the finale.
Salia's jealousy of Ange and desire for recognition from Jill result in her making many poor choices in her attempts to impress the latter. She ends up Driven to Villainy by joining Embryo's forces after he saves her, and even then she continues stubbornly clinging that he loves her when he's clearly obsessed with Ange, and she doesn't realize this until he discards her and the rest to save himself.
For both David and Maine, it's Pride. In David's case, he believes that his high tolerance for cyberware makes him special in the grand scheme of Night City, a want he was always denied as a kid growing up in the poverty of a Santo Domingo Megabuilding. Unfortunately, after the Time Skip he ends up taking on too much cyberware and it, along with personal traumatic events, drive him to cyberpsychosis. As for Maine, he feels compelled to keep installing more and more implants in order to get stronger. His refusal to remove any of them to lighten the mental strain they are inflicting on him leads him to cyberpsychosis and Dorio's accidental death, a moment that triggers Maine's suicidal Despair Event Horizon.
David also lacks any real dreams of his own. He has nothing he truly wants out of life, he just follows the desires of those he gets close to. Because of this, he ends up on a downward spiral of augmentation, attempting to emulate Maine. Even in the end, the closest thing he comes to as far as life goals go is to help Lucy achieve her dream of going to the moon.
For Lucy, it's her inability to communicate with others. Her unwillingness to disclose to David what she found from Tanaka Sr. as well as her one-woman crusade against Arasaka's netrunners strains her relationship with David (on top of his growing addiction to cybernetics). While Lucy meant to protect David, she fails to explain this to him and her actions meant she couldn't rejoin David's crew. Not only does this cause him to question the future of their relationship, but it also leads to her being captured by Faraday, an event that ultimately leads to David's death.
Ruruka's inability to trust anyone, slowly developing into The Paranoiac. The traitor pushes that flaw to the limit by making her NG code "Cannot allow anyone to leave the building", therefore making everyone a possible killer for her. To make matters worse, her boyfriend's NG code is "Cannot put food in his mouth", since she is established to not trust people who don't eat her candy, making her doubt the only one she trusts. This all comes together for her to murder her boyfriend and attempt to kill Kyoko, killing Kohichi in the process.
Ryota Mitarai is a self-admitted spineless coward. Despair reveals that he could've helped stop the Tragedy by telling someone that Junko stole his brainwashing anime, but he didn't because he was too scared. In Future, he eventually decides to brainwash everyone partially because he was too afraid to make like Makoto and fix things the hard way. Junko even gives him a Breaking Speech summing up how his cowardice is going to ruin everything.
Juzo tells Chisa early on that she has a tendency to get too absorbed into things, making her a poor spy. Sure enough, she becomes the mask and grows to genuinely love her students, causing her to abandon her mission and prioritize protecting them instead. This leads to her being captured and brainwashed, then used (as mentioned above) to lure Chiaki to her death.
Light Yagami of Death Note has his overwhelming pride, along with 3 other flaws that stem from this pride.
His massive God complex, which leads him to underestimate his opponents and blinds him to the point where he refuses to even consider the possibility that he could ever lose. Because of this, he is taken completely off-guard when he's finally Out-Gambitted and his lack of a contingency plan spells his doom.
And finally, his bad habit Evil Gloating when he's about to kill an enemy because he has to make sure they know he beat them. He got away with telling Naomi that he was Kira right before the Death Note kicked in and compelled her to walk off and kill herself. He got away with sneering down at L as he died in Light's arms. But when he smugly told Near "I win" just before Mikami's (fake) Death Note conclusively failed to kill all his enemies, he threw away any possible chance of salvaging the situation for himself, sealing his fate.
In Delicious Party♡Pretty Cure, Yui Nagomi/Cure Precious has naivety. Many Pink Cures tend to be oblivious over certain things, Yui takes the cake. She sees nothing wrong with Amane knowing about Recipepes when only she, her teammates, and Rosemary are the only ones who should know about them and is utterly oblivious to Takumi’s crush on her. What takes the cake is the revelation that Godatz can be redeemed, stopping Takumi from striking him down. Instead, Takumi is badly injured when Godatz attacks him in return and forcing Kome-Kome to pull the Cures out, nearly killing herself.
Of special note, Cross Marian's flaw seems to be women and girls. He hates returning to the Dark Order and has been running from them for 4 years. A team is sent to find him. Chief Komui puts Lenalee, a young girl on Cross' team. Cross ends up back at HQ but promptly tries to escape. But Lenalee hugged him and begged him not to leave. He thinks about how cute she is, thus he can't refuse her. And that leads to him attending a meeting, being interrogated for his 4-year absence, investigated, demoted, and put under constant surveillance. His being at the Order in the first place made him easy to find when someone comes to his room to attempt to assassinate him whereupon he's shot in the head. The only reason he went through any of that at HQ is because he didn't run away when he had the chance, and the sole reason he didn't is because a cute girl asked him not to leave. And said girl wasn't even one of his lovers.
Future Trunks in Dragon Ball Z at first appears to have everything together: is a badass, has a tragic past, able to beat Freeza and King Cold like it was nothing. But as the arcs progress, his fatal flaw regarding his issues with Vegeta end up costing him big.
Vegeta himself allows his stubborn pride and arrogance to get the better of him several times, and among other things is the main reason Cell was allowed to reach his Perfect form.
Goku has one that rears its head on occasion: His love for a challenging battle. He projects this desire onto Gohan, who lacks said love, leading to Goku's death.
His mercy has also come back to bite him in the ass. Sparing Vegeta and Piccolo Jr ended up gaining him powerful allies in the end but refusing to just kill the obviously, unrepentantly, mustache-twirlingly evil Frieza has gotten TWO planets blown up and most of his friends killed before a time "rewind" undid it.
Whis points out that in regards to training, Goku and Vegeta have opposite flaws: Vegeta is so wound-up that he refuses to stop training to recover, which weakens him, and Goku is so relaxed that he lets his guard down in situations where Vegeta wouldn't.
Gohan himself has one, as Piccolo points out in Dragon Ball Super: whenever Gohan has a major power advantage, he lets it get to his head and ends up toying with his opponents and letting his guard down. When he battles Cell, despite Goku's pleas to finish Cell off right then and there, Gohan refuses and opts to keep torturing him, leading to Goku's death when Cell decides to Rage Quit and self-destruct. When he battles Super Buu, he allows the creature to retreat and recover, allowing him to return and capture him, Gotenks, and Piccolo.
Most of the villains in fact have the fatal flaw of thinking there is no way they can be defeated. With Vegeta, it was a low-born defeating an elite. Frieza couldn't comprehend (or rather refused to accept) that a "monkey" could become stronger than him. Cell believes his final form is perfect (having the best qualities of each fighter) and thus cannot be defeated. Buu couldn't stand Vegetto's strength. All of them suffer a Villainous Breakdown when they are proven wrong.
Frieza also had the flaw of being too cruel and sadistic to finish off especially hated enemies quickly, preferring to let them suffer before the end. It was this flaw in particular that led to the rise of the first Super Saiyan in more than a thousand years, the one thing that Frieza feared in all the universe and that he'd previously wiped out Planet Vegeta and nearly all of the Saiyan race to try to stop.
Chi-Chi has wrath. She is quick to get angry and often too impatient to stop and think things through. This is why she often tries to stop Gohan (who, admittedly, is a kid) from saving the world, and why she antagonizes Super Buu, who promptly turns her into an egg and steps on her.
Majin Buu's final form, Kid Buu, is noted to be so dangerous precisely because he lacks one, in contrast to his other forms. Fat Buu was childish and innocent, Super Buu was hotheaded and arrogant, but Kid Buu is a pure engine of destruction who doesn't bother playing with his opponents. He can't be befriended like Fat Buu or tricked like Super Buu, only fought to the death.
Zamasu in Dragon Ball Super has a serious case of Black-and-White Insanity; to him, mortals = bad, gods = good. He is incapable of understanding that mortals can change and that the gods can make mistakes, and when the others oppose him, he just pulls a No True Scotsman on the other Kais, considering himself to be the only pure entity in the multiverse. Fusing with himself as Goku Black multiplied that flaw exponentially.
From Durarara!!, Shizuo's severe anger issues and Kida's inability to face his guilt head on. Not only does this put him in a position where he avoids his girlfriend Saki they make up at the end of the anime series but by not facing this head-on, he repeats his whole guilt trip with his best friend Mikado by dropping out of school and leaving Ikebukuro. And Mikado didn't take this well...
Elfen Lied: Lucy's flaw is her desperate need for affection. Having had a horrible life, she wants someone to love her so much that if she even suspects a betrayal, heads will roll. Literally.
In Failed Princesses, Kanade Kurokawa's flaw is her low self-esteem and tendency to put the extremely beautiful Nanaki Fujishiro on a pedestal, even back when Kurokawa hated Fujishiro. As a result, it prevents her from seeing Fujishiro as an equal or becoming closer to her, and causes her to reject Fujishiro's Love Confession.
Erina Nakiri has a serious case of Pride. She looks down on others simply based on their backgrounds, and refuses to admit she might be wrong or back down from an opinion she arrived at without thinking. This leads her to butt heads with series protagonist Soma Yukihira, simply because she refused to admit that a cook from a middle-class diner could make a simple dish on par with gourmet food.
Megumi Tadokoro's is that she's spineless and a Nervous Wreck — prior to the start of the series she was nearly kicked out of Totsuki Academy several times because whenever she's under pressure during exams, she gets severe Stage Fright and panics so much she constantly makes mistakes that make others think of her as a weak student. When Kojiro Shinomiya notices this, he expels Megumi because a chef has to be able to perform under pressure and though Megumi did find a way to work around the substandard ingredients he deliberately provided, she wasn't aggressive enough in grabbing the fresher produce. Megumi is only saved from expulsion because Soma sticks up for her and challenges Kojiro to a food war and Megumi's Character Development is learning to be more confident in herself and to stop relying on Soma to help her out. Overcoming this Fatal Flaw is what impresses Kojiro enough to decide to allow Megumi to stay at Totsuki after all.
Akira Hayama's devotion to his Parental Substitute Jun is both a virtue and a flaw. On the one hand, it allowed him to win during the Fall Classic. On the other hand, when Azami Nakiri took over as new director of Tootsuki and threatened to shut down the Shiomi Seminar (using Jun's lifelong work as a bargaining chip), Akira joined up with him without hesitation, even going against Jun's wishes who warned him that Azami wasn't trustworthy. His refusal to trust others outside the seminar also prevented him from asking Soma and the others for help, which Soma and Jun rightfully call him out on.
Yuki Sohma's fatal flaw is his tendency to hold grudges. He resents his older brother Ayame for often ignoring him as a child and refuses to let him in when he tries making amends, and he'll often antagonize Kyo completely unprovoked out of spite.
Kureno Sohma's flaw is his kindness and Extreme Doormat nature. His curse has been broken for ten years, but he just couldn't bring himself to abandon a crying, desperate Akito and agreed to remain by her side and pretend he was still part of the Zodiac. In the long run, by feeding Akito's clinginess and dependency issues, Kureno only made her overall mental state and attitude worse, and by the time he realizes this, it's almost too late, with both he and Tohru nearly losing their lives trying to reason with her in the midst of a Villainous Breakdown.
The homunculi, as a whole, are firmly convinced that they're invulnerable. While they are much harder to kill than an ordinary human, they're by no means indestructible, and the Philosopher's Stones that power them can only heal them for so long before they eventually run out of juice. In combat, they're more likely simply to take incoming hits and heal rather than dodge, which causes them to burn through their energy reserves faster. Additionally, this belief has allowed the heroes to get the drop on them many times.
Lust’s fatal flaw is her untamed sadism, as she prefers to let her victims suffer horribly instead of pragmatically killing them off as shown by her severely injuring Havoc and Mustang with the latter managing to heal his wounds by cauterizing them with his flame alchemy, sealing Lust’s demise.
Deconstructed with Wrath/Führer Bradley. Unlike the other homunculi, Wrath was once a human who became a human/homunculus hybrid by being forcibly implanted with a Philosopher's Stone; as a result, Wrath lacks the Healing Factor of the other homunculi, but this is precisely what makes him so dangerous. He knows that he will die permanently if he's killed once, and so trained intensely over the course of several decades to become an incredibly powerful combatant. Also, unlike most of the other homunculi, Wrath doesn't stop to brag about how unbeatable the homunculi are in the middle of a fight.
Sloth is slothful, but not exactly in the traditional sense of wanting to avoid work (although he frequently tries to): his main flaws are that he doesn't want to bother thinking things through, he prefers to let other people tell him what to do, and he didn't bother honing his fighting skills. This is why, when he's ordered to go kill Olivier, he makes several mistakes in the resulting fight: he initially doesn't use his real power (Super-Speed) until he has been already severely wounded and has no other choice, said power is way less effective than what it should due to his lack of training, he doesn't think up complex strategies, and he doesn't consider the idea of retreating when things go bad. All because he's too lazy to fight seriously, train, think of a plan, or take the hard route of not letting other people take every decision for him. End result: he ends up in a long prolonged fight that he ultimately can't win.
In Hakuouki, Hijikata's desire to protect Kondou. He deliberately plays the role of the harsh disciplinarian and "Demon Vice-Commander" to elevate Kondou's warm and friendly nature for the troops, dealing with most of the issues and problems instead of Kondou. This backfires on both of them as Hijikata's efforts leave Kondou entirely unprepared to deal with the harsh realities of leadership when the Boshin War began and Hijikata to suffer a Heroic BSoD when Kondou sacrifices himself to buy his men time to escape and is executed.
Arslan's father King Andragoras was overconfident that his powerful army could overcome any enemy with little regard for tactics or planning, despite warnings from one of his generals. That pride would cost him the battle of Atropatene where he not only lost a huge portion of his soldiers, the rest of his followers scattered, the capital city becoming overrun and he himself would be imprisoned.
Silvermask/ Hilmes is obsessed with regaining the throne at any cost. He also easily flies off the handle any time anyone challenges that he might not be the rightful king or if they acknowledge Arslan as the current crowned prince. He does not realize that his temper and violent tendencies are isolating him from potential allies or it might be the reason why people prefer to join Arslan than him. He also does not realize that the Zahhak sorcerers who are assisting him have been deliberately stoking his Hair-Trigger Temper since he was young for him to become an Unwitting Pawn for them to sow further destruction across the kingdom to resurrect their master.
In Hunter × Hunter: Gon's central flaws lie in his temper and impulsive nature. Gon sometimes fails to think things through and such actions lead to him suffering. Though possessing talent far beyond the norm for his age, any time his abilities are challenged, he feels as if he has to prove his antagonist wrong. He continually strives to obtain greater power, often becoming exceptionally stronger in his anger. But Gon's anger also leads to extremely reckless tendencies. When his emotions are ignited, Gon becomes irrational and completely oblivious to anything else. While his will is stronger than most and he can be very level-headed, this clear mind can also make him very cold at times. Even more worrying is the extent to which his simple-mindedness colors his perception of those around him. Often it's difficult for others to understand or relate Gon's actions or thoughts to what people would consider "normal" thinking. On more than one occasion the people around Gon have remarked on how he "doesn't care about the good or the bad" with some believing Gon to be a little insane.
In Magi: Labyrinth of Magic, Hakuryuu's desire to avenge the murder of his father and two brothers is beginning to isolate him from the one person he wanted to protect the most and he would do anything to get power to attain that revenge, including going down the path of depravity.
Alibaba's lack of confidence and self-doubt, especially in the Balbadd arc, made him indecisive which in turn caused problems when he tried to stand up to his older brother the king of Balbadd on behalf of his people.
Maria no Danzai: He does things alone, and ironically, his love for his mother is what kills him in the end and destroys his family. Kiritaka Nagare was a good kid who came from a good family and a loving relationship with his mother. However, he was horribly bullied at school by satanic monsters who tortured him. While it's unknown why he did not go to his teachers and if they would've been any help, he didn't go to his parents because he did not want to worry his mother. So he endured months of torture gathering evidence on his bullies so he could turn them in. Unfortunately, this turns out to be for nothing. In the first chapter, The bullies blackmail him into jumping onto a road, or they will post a fake porn video of his mother on the internet. He was killed by a truck, and his mother witnessed his death. An investigation by the police told his parents that his death was a suicide caused by abusive parents. His mother, Maria, depressed by his death and the reasons given for his death, discovered his journal about the bullying he suffered and swears revenge on the bullying. Two years later, Maria is under a new identity, Maria Akeboshi, and is hunting and killing Nagare's bullies one by one; she throws away her marriage and her previous life to get revenge, which means that him keeping quiet about his bullying and not telling his parents cost him his life and destroyed his family and ironically destroyed his mother when he wanted to protect her and not make her worry.
From Mobile Suit Zeta Gundam and Mobile Suit Gundam ZZ, Haman Khan's fatal flaw is despair. She Used to Be a Sweet Kid, and she could have become one of the greatest heroes of the Universal Century. But due to Char going off to play soldier and finding herself as an absolute dictator of a generally-pretty-evil bunch at fourteen, she grew disillusioned with humanity and came to believe that they deserved nothing more than an absolute dictator. This led to her death, as well. When she fought Judau to a draw but failed to defeat his ideals, she gave up and killed herself.
Midoriya's Chronic Hero Syndrome and his fixation with trying to emulate All Might in every way ultimately does more harm to his body than good. His right arm ends up badly scarred and it reached the point where his hands become permanently disfigured. And the doctors tell him that if he takes any more significant damage using One For All, he could potentially lose the functionality of his arms altogether. His mother's concern, a pep talk from All Might, and his inability to rescue Bakugou because of how he crippled himself from an earlier fight finally got Midoriya to reconsider how he uses his Quirk going forward.
For Bakugou, Pride and wrath are his two big ones and they're well-connected to his unexpectedly fragile ego. Whenever he sees something that could be construed as pitying him or suggesting he's not the best, he will immediately lash out. This is the reason he has very few friends at school and it's a massive stumbling block when it comes to his career as a hero, as he can't properly accept the public service part of heroism and has an unfortunate tendency to be a Leeroy Jenkins. It took the fall of the civilized society for him to realize these flaws.
Jealousy is another; as soon as he saw the slightest sliver of someone being more competent at his work than he was, or anything at all that he perceived as an advantage, he'd immediately become disconcerted. He feels this towards Midoriya more than anyone, because the latter was formerly Quirkless, but now enrolled in his very school and receiving the kind of validation Bakugou never had, in spite of all the praise heaped on him as a child. Fortunately, he curbs this negative emotion as he continues to mature.
His It's All About Me attitude. At the start of the series, while Bakugou was strong and determined, he was also very arrogant and self-centered. He only ever focused on himself and disregarded others, making him very unpopular with his peers, who constantly called him out on it. Luckily, as the series progresses, Bakugou learns to stop making everything about him and show more empathy to others.
Sasuke's need for vengeance has caused him to abandon his friends, home, his arm, and be called a missing-nin. At the end of the series he chooses to Walk the Earth to atone for all the pain and suffering his quest for revenge caused.
Sakura has two:
Thanks to her intelligence, there are times she can be very imposing and patronizing, even after her Character Development. Not so bad unless that is combined with her stubbornness, temper, passive-aggression, and selective hearing tendencies, then she can be rather off-putting at times, which can lead to...
Her immense sense of guilt from being more in touch with her feelings, but not having the same control, causes her to make rash actions and decisions with tunnel vision. She is especially sensitive and emotional when it comes to Naruto and Sasuke, to the point where it also causes her to be stubbornly reluctant to share certain information, which can be why Kakashi isn't always willing to share certain info with her at times.
Played for Laughs. Jiraiya's perverted nature has led to him being tricked (e.g., Naruto, the Akatsuki) or severely beaten up (e.g., Tsunade).
Deidara's is Pride, being so obsessed with his art and showing off that he pretty much self-destructs just to impress Sasuke.
#* Neon Genesis Evangelion: Whether it be Shinji's raging inferiority complex, Asuka's self-endangering recklessness, Misato's alcoholism, SEELE's bizarre neo-mystic delusions, or Rei's complete disregard for her own life, pretty much everybody has at least one of these, and quite a few have more than one. (ZCE- please explain how these flaws are demonstrated in the story.)
In New Game!, Tsubame "Naru" Narumi suffers from tunnel vision when it comes to getting hired at Eagle Jump. Her parents, who'd rather she inherit their Ryokan (inn) inn, forced her to pay her own way through school and telling her to come home if she doesn't get a job at Eagle Jump, resulting in feeling pressured. As a result of this drive to succeed, Naru looks down on Nene (who'd been hired at the same time despite not possessing all the qualifications) for seemingly not being as committed to the job they share. Naru's long-time friend Momiji "Momo" Mochizuki also observes that Naru vetoing a change to a minigame's specs just to make sure they don't go over a deadline is unlike her. It ultimately culminates in Naru rushing through checking her code, resulting in her minigames having many bugs, and her and Nene scrambling to fix them. Naru being humbled by that experience, along with getting hired at Eagle Jump, helps her get over this flaw.
Bishamon's refusal to accept consequences of her actions in Noragami. She regularly takes in more Shinki than she can to protect them despite the strain and the danger it puts on her. When the Ma clan was destroyed by Yato as a Mercy Kill, she refused to acknowledge her own failing which led to the clan being corrupted and blamed Yato instead. She consistently insists that she is fine when she is not, causing in turn her Shinki to hide their own problems because they don't want her to worry, resulting in their hidden anxieties straining her body further.
Luffy has one true fatal flaw: personal loyalty. The length of which he's willing to go to help a friend is nothing short of incredible. This may manifest as stubbornness, anger, and inconsideration. For instance, his inability to control his volcanic rage eventually leads to Kuma attacking and scattering all the Straw Hats around the world. Luffy does what he wants, even if he knows there would be grave results. The above example had Hatchan making Luffy promise not to cross paths with a World Noble, regardless of what happens. But when Camie and Hatchan are kidnapped and injured, Luffy went ahead and broke his promise and while he did apologize, he didn't show any regrets.
Usopp has his inferiority complex due to his belief that he is not strong or useful to the crew, which is mostly comprised of people with Devil Fruits or Charles Atlas Superpower, something that comes to a head when Luffy decides to replace Going Merry. Not only was the ship a gift from Usopp's friend Kaya, but Usopp was responsible for maintaining the ship to the best of his limited ability, and he blamed himself for being robbed and losing most of the crew's money, resulting in him taking the decision personally and thinking it was his fault. Usopp being too upset to think clearly, combined with some poorly thought-out remarks by Luffy, results in Usopp deciding Luffy won't need him anymore, leaving the crew and dueling Luffy for the Going Merry.
Ace can be a hothead when it comes to Whitebeard being insulted. When Blackbeard kills a crewmate to steal his Devil Fruit power, Ace goes off on an unauthorized mission to hunt Blackbeard down, leading to him being turned over to the Marines and sentenced to death. This results in a massive war as Whitebeard's crew assaults Marineford to save Ace, and when Akainu, one of the three Marine Admirals, insults Whitebeard, Ace halts his escape to fight him. Since Akainu's magma-based Devil Fruit powers are a counter to Ace's fire powers, Akainu is able to overpower Ace, and kills him when Ace ends up Taking the Bullet for Luffy.
In The Promised Neverland, Lord Bayon's flaw is Gluttony. He found cattle-grown humans to be tasteless and secretly arranged for hunts in his grounds and at first, very sparsely. But his desire to consume such delicious food made Bayon indulge himself more and more and made the hunts into grand events. However, by frequently shipping in children to replenish those killed, this would lead to a resistance forming and they would be the ones to kill Bayon.
Puella Magi Madoka Magica: Mami's is Loneliness; it made her reckless over the prospect of gaining companions and mentally fragile. Sayaka's flaw is pride and idealism; the former prevented her from accepting the unworkability of the latter until it's too late. Kyouko's is selfishness; it drove away the one person she came to care about. Madoka's is selflessness and self-sacrifice; she wants to become a Magical Girl to help others, which has a fatally high cost.
Puella Magi Madoka Magica The Movie: Rebellion: Madoka's is Heroic Self-Deprecation; which led Homura to believe that Madoka didn't really want to make her Heroic Sacrifice from the series, pushing Homura off the deep end to undo it. Kyubey's is Greed and Lack of Empathy; they try to bring back the horrific, but higher-yield Witch system but fail to realize how far the Magical Girls would go to stop them. Homura's I Work Alone and Ineffectual Loner tendencies left her unable to trust get help from those she needed it from, even her Witch form has self-reliance as her nature, and her Silly Rabbit, Idealism Is for Kids! mindset left her unable to accept Madoka's sacrifice and betraying her to take her back.
The Quintessential Quintuplets: Each of the Nakano sisters has a notable flaw that flares up to stir conflict at least once in the story:
Ichika sometimes takes her role as the Cool Big Sis in watching out for the others too seriously, to the point she tends to bottle her own feelings and neglects to take care of herself. This reaches a head during the Sisters' War arc when, unable to cope with her own feelings, she decides to sabotage the other's efforts to try and increase her chances to hook up with Fuutarou herself.
Nino has a tendency to be Innocently Insensitive, rarely being receptive to other people's feelings and often acting out on her own without any care for the potential consequences. Case in point, she kicks off the Seven Goodbyes arc by actively trying to pick a fight with Miku so that Fuutarou leaves, which results in getting a slap from Itsuki when she crosses the line.
Miku's lack of confidence. She often compares herself unfavorably to her sisters, and while she can be very dedicated when she sets her mind to something, she tends to self-impose additional conditions to motivate herself more (such as deciding to confess to Fuutarou if she gets the highest grades), and when she's unable to fulfill them, it hurts her already fragile self-esteem.
Yotsuba has a massive Guilt Complex. She tends to drag her own mistakes from the past, thinking that she's become a huge burden for her sisters, and often also blames herself for things they do if she thinks she had a hand on it, such as the aforementioned Ichika incident, as she was the one to tell Ichika that she should be more selfish in her pursue of Fuutarou.
Itsuki's Pride causes her to reject Fuutarou's tutoring, due to their bad first encounter, even when it's clear that studying on her own is not helping her one bit. To a lesser extent, she also has a habit of trying to act more mature than she actually is, but her temper always flares up and the facade breaks apart.
Tenma always wants to make others feel better. This almost gets her killed in the manga.
Eri is a Clingy Jealous Girl. A hint of Harima getting paired with a girl sends her into a quiet rage which almost messed up her friendships with Mikoto and Tenma, and in the manga almost gets Tenma killed.
Death the Kid has his Obsessively Organized tendencies and self-esteem issues; the presence or lack of symmetry in his surroundings (or remembering that he may have forgotten to symmetrically fold his toilet paper roll this morning) can take him out of a battle in a heartbeat. In one case, Liz uses this against him to avoid getting into a battle in the first place, as the factory containing the Clown scared her, (and with good reason). She does something similar earlier when taking note of Free's ball and chain to provoke Kid to attack the werewolf.
The origin of his OCD is revealed: Shinigami-sama was a Great Old One who possessed the Madness of Order, much like how those like Asura possessed Madness of Fear. All the Great Old Ones can radiate and control their Madness, as their sheer existence and power is so mighty, surrounding beings go mad. As such, there is a need to bring order and those who succumb to it can force humanity to be mindless puppets. Death the Kid's OCD appears to be an offshoot of inheriting this form of Madness.
The Salvage arc suggests that potentially each of the Great Old Ones has one of these which would make exerting compulsion in them a valid tactic against Physical Gods.
In Tiger & Bunny, Kotetsu has a noted tendency to keep personal struggles to himself, even when those personal issues don't just affect him. This starts really coming down hard on him in the second half of the series when he can't work up the nerve to tell Barnaby he's retiring, or the reasons behind it, and Barnaby takes it as a sign that he doesn't trust him.
And Barnaby has his own flaw: the hell-bent obsession with revenge that made him an Ineffectual Loner who has rejected any close personal relationships for the past 20 years.
It becomes clear pretty quickly that Satou's biggest flaw (Hikikomori tendencies aside) in Welcome to the NHK is his incredibly addictive personality, marked by him hurling himself headlong into anything he's introduced to (internet porn, MMORPGs, etc.) and needing to be bailed out by others.
Yami Yugi has his Pride where he feels that he has to win at all costs, even if he has to do questionable things, such as being prepared to kill Kaiba during their rematch in Duelist Kingdom to save Yugi's grandpa. He mostly grows out of this as seen in his Battle City duel with Bakura where he refused to attack the injured Bakura. It resurfaces in the Awakening the Dragons arc, though, where in a duel with Rafael, Rafael uses Exchange to hand Yami the Seal of Orichalcos to goad him into using it. Rather than accept a loss for a no-risk duel, Yami activates the seal himself, becomes corrupted, and loses Yugi's soul when Rafael defeats him.
Seto Kaiba's flaw is his obsession with being the best, at everything, and indeed, some have used his need to defeat and surpass his rival as a way to manipulate him, or try to. Kaiba's obsession can often keep him from thinking clearly and taking needless risks in pursuit of his goal. He would likely find life more enjoyable if his need to be number one didn't dominate him. This comes to a head in Dark Side of Dimensions where his obsession with beating Yami Yugi causes him to try and bring back the puzzle pieces and almost got him and Yugi killed when they are targeted by Aigami/Diva
Yu-Gi-Oh! GX: Juudai's stubbornness, being headstrong, irresponsible, impulsive, and impatient is cute and endearing for two and a half seasons. Then all of those combine and (he thinks) gets four to five of his best friends killed.
Yu-Gi-Oh! 5Ds: Yusei's hesitance to duel against someone that was once his friend.
