There's several anime that are very critical of America, its history, and foreign policies. Anime was inspired by Disney, an American company. Crossing over with hypocrite, the amount of anime that's honest about Japan's checkered past is very small.
Reiner in Attack on Titan is described by his instructor as having incredible willpower and mental fortitude and others rely on him, considering him stable and reliable. Not only is Reiner a mole, he is the Armored Titan who is completely invulnerable due to his armor plating and is mentally and emotionally unstable due to Becoming the Mask and is the least sane out of the Titan infiltrators.
Eren has an all-consuming hate for Titans. He finds out he is a Titan shifter and several friends turn out to be the very Titans he hated the most—and worse, he became a Titan Shifter by eating his dad, who was also a shifter. Furthermore, Eren has the ability to command regular Titans.
Human characters struggle with becoming monsters to effectively fight against the Titans. The monsters (Titan shifters) struggle with their humanity which decreases their ability to fight effectively.
Bleach had a moment of irony during the Fake Karakura Town arc. Kaname Tousen had been fighting Sajin Komamura and revealed that he had gained Hollow powers which, to Tousen's surprise, allowed him to see. However, as he was about to finish Sajin off, Hisagi attacked from behind, before remarking that Tousen would've dodged the attack easily if he hadn't been distracted (and, in effect, blinded) by his newfound sight.
Index had her memories erased regularly, to prevent them overloading her mind (actually a lie to keep her under control). Touma removes the need for this only to get his memories erased. By a (brainwashed) Index, no less.
Accelerator kills over ten thousand Sisters with the goal of increasing his own power. After being stopped, he later chooses to save a particular Sister. He devotes all of his power to doing so, which drops his normally-impregnable defense and allows someone to shoot him in the head. He survives, but with brain damage that would normally leave him unable to walk, talk or use his ability. To regain these functions, he's dependent on a device that uses the brainpower of the very same Sisters he'd been killing.
Mikoto sees one of her clones get brutally murdered by Accelerator. There's a brief flashback to before she knew about the clones, discussing the possibility with Kuroko.
Kuroko: What would you do if a clone of yours appeared before you? Mikoto: Ah, that would freak me out. I think I would wish it would just disappear. [present]: Mikoto goes ballistic on Accelerator
One of the Breather Episodes of the Sisters arc involves Kuroko learning that it's okay to rely on her friends, and that trying to do everything herself just causes problems. Cut to Mikoto, who is fighting a one-woman war against the Level 6 Shift project.
A case occurs early on when nobody can figure out who Zero is, but Lelouch almost gets unmasked by a cat.
Two episodes after her declaration of The Power of Love and just one right after she finally requites her own love for Lelouch, Wrong Genre Savvy Shirley is killed by Rolo. Especially ironic in that she could have saved Lelouch from the path he would go down in the subsequent arc and that her death was a catalyst for much of it.
Also ironic that after the "Orange Incident", Jeremiah was told by Guilford that his options were to continue working as a grunt or go work on an orange farm. His profession after Lelouch's death? He works on an orange farm with Anya.
On a smaller scale, the main antagonist of the story is the world's most powerful superpower, the Holy Britannian Empire, which, despite controlling over a third of the world at the start of the series doesn't actually control Britain.
Lelouch's entire plan to save the world was based on an attempt to make it "gentler" for his sister Nunnally. He cares about this plan so much he sacrifices his own life for it, but as he lies dying in front of her, she tells him that the only kind of world she ever wanted was one where they could live together.
Also ironic is that at the beginning of the series, Lelouch took on the title of Zero, to become a symbol of Justice against the Britannian emperors tyranny, while Suzaku had joined the military hoping to change Britannia from within. At the end of the series, Suzaku and Lelouch had Their roles switched. Suzaku became Zero, as a symbol of Justice, never to live again as Suzaku Kururugi, while Lelouch became the Britannian Emperor, and gave his life in the process of changing the system from within.
Prince Clovis became viceroy of Area 11 in order to make it peaceful for his deceased brother, Lelouch. Lelouch isn't dead, Clovis is an incompetent ruler—which he realized—and through his incompetence, Area 11 grows more violent. And Lelouch is the one who assassinates him for it.
Jeremiah Gottwald is dead-set on his mission to assert Britannian superiority against the rebellion because he believes that it's what Lady Marianne and her children would want. The masked terrorist who has him disgraced is actually Lady Marianne's son. Though he remedies it in the second season. Note the parallels between the parade scenes in season 1 stage 4 and season 2's final turn.
While Hell's Gate dolls powers out at random in Darker Than Black, it seems to have a strong sense of irony in terms of who gets what or what price they must pay. Examples: the lesbian Mina Hazuki must kiss men as her Remuneration; November 11 abhors smoking, so that's naturally what he must do every time he uses his powers; August 7's Reality Warping powers would sure have come in handy in his profession as a magician if he didn't have to reveal the secret behind a similar stage trick immediately after; and the one Contractor who gets to temporarily regain her conscience and humanity as her price? Her power is liquefying people's internal organs.
DARLING in the FRANXX has a tragic case. In Episodes 12 and 13, we learn that Zero Two met a little boy when she was a little girl. She thinks killing enough Klaxosaurs will make her a human and let her stay with that boy, and she doesn't care how many partners she has to kill in the process to do it. We learn this during a flashback while she's killing her current partner, Hiro, who happens to be the boy in question.
In Digimon Adventure 02, Paildramon is struggling against Triceramon and Mummymon, but he's able to evolve to his Ultimate/Mega level Imperialdramon by the power of Qinglongmon and overpowers Triceramon very easily. We later learn in Digimon Adventure tri. that Qinglongmon evolved from a Triceramon.
Dororo: The conflict of the story is ultimately started when Daigo Kagemitsu wishes on the forty-eight demon statues in the Hall of Hell for the power to wage his war and conquer Japan. The epilogue notes that the flames of that war eventually reached the Hall, burning it down and destroying the statues.
Commander Red hiring Mercenary Tao to kill Goku ended up destroying the Red Ribbon Army since Tao killed Bora on a whim, which made Goku go after all of the Dragon Balls. Before then, Goku was only interested in the 4-star ball.
One has to be familiar with Dragon Ball Z to fully appreciate the irony of the Goku versus King Piccolo fight. Both are aliens who have long forgotten their real names and were sent to Earth to save their lives. The big twist, Goku came from a race of ruthless warriors who were also planet destroyers. Piccolo, or more correctly the Nameless Namek, came from a peaceful, benevolent race. After becoming infected by humanity Goku became a good person while Piccolo became corrupted. In another world and time, Goku would have been the conqueror and Piccolo would have been the savior. Piccolo Jr. even points out the irony of dedicating his entire life to avenging his father and killing Goku, only to die protecting Goku's son.
In the manga, Piccolo toyed with the idea of corrupting Gohan and turning him against his father. But instead, the opposite ended up happening with Gohan's Incorruptible Pure Pureness changing Piccolo and him becoming one of Goku's True Companions.
Frieza wiped out all the Saiyans because he was afraid that he will be beaten by a Super Saiyan. He was defeated by Goku, and ultimately killed by Future Trunks, both who are Super Saiyans. The true irony in the former case is that it was Frieza's own actions, killing Krillin and Vegeta, nearly killing Piccolo, and threatening to kill Gohan drove Goku into the Super Saiyan state. In essence, if Frieza hadn't been stupid enough to twist the knife, he probably wouldn't have had to deal with the thing he was most afraid of.
The Episode of Bardock special reveals that Bardock was sent back to the past and became the Legendary Super Saiyan. Meaning that Frieza was responsible for creating the very legend upon which he destroyed the Saiyan race for, and eventually his own death.
In Dragon Ball Minus it is revealed that Frieza recalled all the Saiyans to their home planet so he could kill them all at once. This clued Bardock in that something was wrong and sent Goku into space to space. If Frieza hadn't decided to give the order, Goku would have never left Vegeta.
Bojack's last words are "you fool, any last words before you die?!"
In the Cell Saga, Cell exploits Vegeta's pride and Blood Knight tendencies to convince him to attain his Perfect form to have a better fight, upon which he utterly trounces Vegeta. Afterwards, Trunks tries Hulking Out to take on Cell, only to discover that his increased muscle mass made him too slow to actually keep up with Cell, a realization that Cell quickly mocks him for. In the Cell Games, Cell's own pride and Blood Knight tendencies are what lead him to deliberately piss Gohan off enough to reach Super Saiyan 2 to have a better challenge, upon which Gohan utterly trounces him. Furthermore, during his Villainous Breakdown, Cell tries Hulking Out himself to beat Gohan, only to be too slow to actually do so; in this case, Trunks even flat-out states that Cell is making the exact same mistake that he had previously mocked Trunks for.
Despite Vegeta's desire to become stronger than Goku, the latter has never actually defeated him. In almost any match they fought is either interrupted or have Vegeta gain the upper hand. So the only reason Vegeta actually wants to be better is simply wounded pride that Goku could suddenly become better than him.
Krillin was the only character to die in every show of the franchise until Dragonball Super. Not only does he survive that show, but he doesn't even die in one episode where the entire Earth is destroyed.
At the end of the Tartaros arc, it's revealed (to the audience) that the most powerful of the demons from the Books of Zeref, E.N.D., is the amnesiacNatsu Dragneel. Of whom Mard Geer (E.N.D.'s faithful Dragon, who was trying to revive him) spent most of the last act of the arc trying to kill. The only one even aware of the irony of the situation is Zeref himself.
The Fiore Royal Family blames Zeref for Acnologia's transformation into a dragon. That's actually the one thing Zeref isn'tresponsible for in some way. For further irony, a lot of things Zeref was responsible for were the results of his plan to defeat Acnologia.
In Fullmetal Alchemist, Truth appears to like irony. Edward wants to support his family, so Truth takes his leg. Alphonse wants to feel his mother's embrace, so Truth takes his ability to feel. Izumi wants to have a child, so Truth takes away her fertility. Mustang has a vision for the country, and Truth takes away his eyesight. Father/Dwarf in the Flask/Homunculus didn't want to be a prisoner to anyone so Truth traps him behind the Gate of Truth. See a pattern?
It's pretty ironic that Ax-Crazy Gauron of all people would call Gates "one hell of a nutcase." Especially considering that he was perfectly serious when he was saying it. And yes, this is coming from the man who canonically wanted to kill Sōsuke and "fuck his corpse up the ass."
When it comes to Gauron, irony pulls double shifts. For instance, within Amalgam (an organization whose main members all have code names of metals which are chemically able to form amalgams with Mercury), Gauron's code name is Mr. Iron, a metal that is, in fact, not able to amalgamate with mercury at all. (It is, however, very resilient and highly magnetic). It is mentioned in the later novels that Gauron had been given this name as a petty little in-joke, meant to set him apart as "not really one of us". After TSR, though, it became painfully obvious that the joke was in fact on Amalgam, as Gauron betrays them to Sōsuke. The consequences of his betrayal are still being felt a couple of novels later. Not one of us, indeed.
Yet more irony that involves Gauron: In Sōsuke's life, it seems that every single one the men who eventually became close friends with him started out as his mortal enemy that he was trying to assassinate. Examples: Majid, whom Sōsuke was sent to assassinate (though his attempt failed), only to take a liking to Sōsuke and adopt him as his own son. He was described as an incredibly kind foster father to him—someone Sōsuke would always respect. Kalinin, whom originally was Sōsuke's enemy, since he was in the KGB and Sōsuke was an Afghan Guerilla—Sōsuke even tried to kill him, only to get kidnapped by him. Again, Kalinin treated him well, and liked him ever since the beginning (as he took a liking to Sōsuke ever since he rescued the boy as a baby), eventually resulting in Kalinin legally adopting Sōsuke as his son. Kurz, who was revealed to have been hired as a mercenary on the opposite side of Sōsuke in Lebanon, before either joined Mithril. They almost ended up killing each other, and ended up developing a great amount of respect for each other, each claiming that the other was the strongest opponent they faced (despite being in Arm Slaves, meaning they didn't even see either's face). And then there's Gauron who was actually one of the few main male characters who met Sōsuke not as an enemy. And it was Love at First Sight for the crazy guy, resulting in his attempt at picking the boy up and taking him to his camp, which was rejected. And so, despite being one of the few guys who first met Sōsuke on semi-amiable terms, he turns out to be the guy Sōsuke hates most.
Miaka of Fushigi Yuugi is not fond of books very much. And then she ends up in one.
In Hayate the Combat Butler, Hayate does not believe any girl could ever like him. The dramatic irony here is, EVERY girl likes him. Situational irony also occurs in the manga on Valentine's Day, when Hayate is talking to Maria. Hayate tells her all the reasons he feels like he will never get a girlfriend (Which are identical to the reasons she doesn't have a boyfriend) and believes he is not in any position to ever get one. Maria contemplates this afterward and realizes that the only man she can get and is interested in is Hayate. Too bad her Ojou is also interested in him.
Kaguya has the largest number of siblings in the entire cast (with three older brothers), yet she had the loneliest childhood.
At the start of the series, Kaguya has a very low opinion of Ishigami in comparison to how she views Shirogane (her crush) and Fujiwara (her "best friend"), to the point of thinking that she views him as little more than an insect. Jump forward about a hundred chapters, and he is the one who she feels the most at ease around due to the two of them having developed a Like Brother and Sister dynamic.
Fujiwara is an Omniglot, yet Japanese is her worst subject.
Maki demonstrates herself to be incredibly artistic during the culture festival, yet Art is the only subject that she didn't an A in on her last report card. Meanwhile, Fujiwara (who is a Terrible Artist) did get an A.
Maki is the one character in the series who is shown to outright dislike Kaguya. Naturally, two of her closest friends are the resident Kaguya fangirls Karen and Erika. This is due to the fact that she has spent most of her life being compared to Kaguya and actively comparing herself to her, being a "Shinomiya" but much more familiarly removed than Kaguya.
Kaguya is established as being a Clingy Jealous Girl in regards to Shirogane, getting worried whenever another girl is shown to be close to him. When she discovers that Moeha (whom she has previously been established has having a hard time interacting with) also has a crush on him, the two of them use it as a bonding experience as they both gush about all the things they like about him.
Miko, in spite of being on the public morals committee, is shown to have the absolutely kinkiest thoughts of anyone in the student council.
One of the series premier Running Gags is Shirogane imagining Kaguya giving him a condescending "How Cute" over any sign that he likes her. The one time she actually does this, it's because he isn't acting on his feelings for her.
Kamichama Karin: Kazune has the power of the sun god Apollo, but he sunburns easily. Micchi has the power of the sea god Neptune, but he can't swim at all.
Rokudo Mukuro's main goal is to pull a Grand Theft Me on Tsuna and then proceed to destroy the mafia, and yet Daemon Spade's whole plan consists of doing the same thing, only via taking over Mukuro instead of Tsuna.
Tsuna is the only one who can see through Reborn's various Paper-Thin Disguise when no one else can. In later chapters, he is the only one who doesn't recognize Reborn's adult form.
Kill la Kill: Satsuki Kiryuin mocks Ryuko Matoi for having a goal as base and meaningless as avenging her father's death. Satsuki's own goal is to avenge her father and baby sister, who were both killed by her mother. Ryuko is that sister. Their father secretly saved her, then faked his death and took on a new identity to raise her.
Fate spent most of the first season as a criminal being pursued by the TSAB due to her attempts to earn the love of her psychic mother. Not only did she grow up to be a highly respected member of the TSAB, she was Happily Adopted by the captain of the TSAB ship that captured her.
In the original Triangle Heart 3: Sweet Songs Forever continuity, Nanoha's father died before she was born. In the main Lyrical Nanoha continuity, she's the only major character to be raised by both of her biological parents.
Nanoha (a huge proponent in The Power of Friendship) was born on March 15th (a day most famous for a guy being murdered by his friend). To take the irony even further, it's also the day of a Shito festival that features the procession of a giant wooden phallus, and she's a lesbian.
Despite being a literal clone of her "older sister" Alicia (complete with Genetic Memories), Fate has far more in common with her adoptive brother Chrono in terms of personality.
The Wolkenritter were the ones who gave Hayate the will to live, yet they were -through no fault of their own- the cause of her terminal illness. To make it even more ironic, their plan to save her life would have killed everyone.
Hayate spent a good chunk of her childhood as a friendless orphan, yet she was at her absolute loneliest while literally surrounded by friends and family.
At the end of the season, Hayate says that she'll be Nanoha and Fate's junior in the TSAB. Come StrikerS, she's their superior officer.
Similarly, Subaru being a combat cyborg makes her the least normal of the Forwards, yet she was the only one with a normal childhood.
Dieci wondering if Nanoha is even human after the latter Curb Stomps her is a double case of this. Not only is Nanoha one of the only mages at her level who is a baseline human, but Dieci herself is a genetically modified combat cyborg.
During the attack on the Ground Forces HQ, Otto and Deed were responsible for kidnapping Vivio. Guess who end up joining the Saint Church (which worships the woman that Vivio was cloned from) after their Heel-Face Turns?
Erio views Fate as a mother and Caro sees her as an older sister. From a legal standpoint, she's Caro's mother and Erio's sister (since she was too young to formally adopt him).
Despite being the Token Good Teammate of the Numbers, Dieci ended up having one of the longest sentences among those who underwent a HeelFace Turn (second only to Cinque, who was guilty of at least one murder).
She also accuses Vivio of being a spoon-fed girl by birth who never experienced any hardship, unaware of the fact that Vivio is adopted and had gone through a hellof alot worse than the bullying that she had to deal with.
Jill believes that Hard Work Hardly Works, which puts her at odds with Nove (who thinks than anyone can excel at martial arts if they have the right training). Jill is a baseline human who earned her skill via Training from Hell, and Nove is a combat cyborg.
A consistent part of Nanoha's backstory across every single continuity is that she comes from a family of skilled swordsmen. The only continuity where she has said swordsmanship training is INNOCENT, a series where all the fighting is in a virtual reality card game that would render said skills useless.
In addition, it is correct to assume that growing up in a family of swordsmen would make Nanoha skilled in melee combat, especially with swords. However, in all continuities, Nanoha acquires skills and becomes very proficient in ranged combat.
Fate's last name translates to "redhead", but she doesn't have red hair (and neither do her mother or older sister for that matter). The ironic part is the fact that just about everyone else in Fate's life is a redhead (her familiar, her "best friend", her rival, two of her adoptive children, and her apprentice).
While secretly investigating Magnostadt as a student and forced to hide his powers, Aladdin is remarked to possess "just above average" magoi. He is actually one of the Magi who is able to use and wield unlimited amount of magoi.
Hakuryuu is presented as a contrast to the rest of his siblings who are war-mongering and imperialist. Then it turns out he could care less about the Kou empire and only wants to kill his mother for murdering his father and two brothers, not caring who stands in his way, leading him down a dark path and making him worse than any of his siblings.
In Mazinkaiser, the Mycene send one of their generals to attack Koji before he can ride his mecha, Mazinkaiser. Said general is stopped by someone piloting a different mecha. Thus, the plan to kill The Hero before he gets on his mecha is stopped by a Joke Character riding a mecha.
Tohru is a chaos aligned dragon who hates gods, yet she has dedicated her life to serving as Kobayashi's maid (a job that involves keeping things orderly) and one of her closest friends is a (former) goddess.
Elma is a harmony dragon who's supposed to keep order, yet her introduction featured her causing chaos by smashing through the wall of Kobayashi's apartment. By contrast, all of the Chaos Dragons (and the one neutral one) were polite enough to use the front door.
Chapter 28 of Kanna's Daily Life ends with Saikawa telling Kanna that supernatural creatures don't exist. Her saying this is accompanied by a shot of people walking along the street, every single one of which is known by the audience to be supernatural in some manner.
Early on in the series, Duo locates the sunken, damaged Wing Gundam and decides to take it for his backup supply. Two episodes later, Wing has been salvaged but needs to be repaired overnight for a new mission despite a lack of spare parts. Heero manages it anyway, which amazes Duo until he finds out that Heero stole the needed parts from his Gundam, Deathscythe. Though Duo's reaction is only aimed at the treachery because he was complementing Heero's work just moments prior.
My Hero Academia: Bordering on being insulting, despite superheroes being created by Americans, in this manga Japan is the number one place in the world to train to be a pro hero and apparently has the best pro heroes in the world. This despite that, in-universe, the first country where Quirks appeared was China, so you'd think they'd be the experts.
In the Chuunin Exams arc, the exam participants are given an extremely difficult written test; so difficult, in fact, that most of the participants are forced to cheat in order to pass. The only participant who is shown not to have cheated is Sakura Haruno, who is smart enough to understand and answer the questions fairly. As it turns out, the point of the test was to see how skilled the participants were at secretly gathering information i.e. how well they could cheat without getting caught. In other words, Sakura passed the test by unwittingly ignoring the actual objective of the test. Naruto didn't know any of the answers, but still refused to cheat and managed to pass due to the Secret Test of Character, so he also passed despite ignoring the actual objective of the test. He passed by turning in a blank test, which is also ironic.
The first time that the village openly showed respect for Naruto was after his fight with Neji, a fight that he won by using the same power that they hated him for. And the point where he was accepted as a hero was during his fight against Pain, where he gave into the power of the fox (the very thing that people were afraid of the entire time).
Tobi mocks Kakashi's Sharingan as a "borrowed power", while he was himself fighting with five borrowed powers at the time, namely Hashirama's cells, Madara's Rinnegan, Madara's chakra rods, six jinchuriki zombies resurrected by Kabuto, and six tailed beasts. He had even been using a borrowed name for a long time.
After the Final Battle with Sasuke at the series' end, Naruto's longtime goal of having Sasuke acknowledge a loss to him gets fulfilled, the latter admitting defeat in the face of Naruto's determination. However, Naruto not only doesn't care about that at this point but actually gets angry at Sasuke for seemingly acting like it's still a matter of winning or losing.
Naruto has the ability to transform into an army of naked women and spent years with Jiraiya, a huge pervert. You'd think he'd notice that arguably the most beautiful girl he knows, Hinata, is attracted to him.
Monkey D. Luffy's first voyage as a pirate was to drop Coby off at a base to become a Marine.
The main reason why Buggy didn't join Shanks twenty-two years ago was because he believed Shanks didn't have what it took to make it as a pirate due to his personality. Fast forward to the start of the series and Shanks is one of the four most powerful pirates in the world while Buggy is raiding small towns in East Blue, the weakest sea.
In Sanji's flashback, him and Zeff narooned on an island, and Zeff had a bag of treasure with him. Naturally, having all the money in the world doesn't matter when when you're dying of hunger.
Zeff: Having money but nothing to eat. Funny story, don't you think?
This was how most of Doflamingo's executives are defeated. Sugar who can create toys is defeated by a toy. Machvise (whose fighting style is basically slamming his enemies with downward force) is sent flying upwards. Diamante is taken out by a gravestone of a person he had murdered. Trebol's No Sense of Personal Space backfires on them when they decided to crush their opponent up and personal and said opponent used their power to cut their chest. Pica attacked all the weakened fighters to prevent them from attacking him but by turning his back on the remaining fighters, they combined strengths to defeat him.
After the Dressrosa arc, Usopp's new bounty (200 million) is higher than Franky's, something that annoys the latter. The irony? Usopp's bounty is the same amount of Berries that the Franky Family stole from him back in Water 7. Knowing Oda, it was more than likely intentional.
A lot of this in the series, though a big one is probably how Tamaki spends a good lot of the show fantasizing about a girly Haruhi and doing his best to transform her into such and continuously failing, all for randomness and comedic purposes to the viewers/readers. However, as the story progresses and Haruhi finds herself in love with him (while he remains completely clueless to this), she gradually turns more into a woman, all on her own. Benibara from the Zuka club points this out in Chapter 82, shortly after Haruhi and Tamaki have become a couple, that she now "totally and utterly looks like a girl". So in the end, Tamaki did succeed in making Haruhi more feminine; it just happened when he wasn't trying to.
Also, when Haruhi first realizes her feelings for Tamaki, she briefly gets depressed when thinking how she looks like a boy and subsequently thinks how Tamaki only sees her as his daughter.
This is played straight when a transfer student named Kanoya arrives at their school, who is introduced when Tamaki saves her from getting kicked by a horse, causing her to crush on him and continuously sticking with him the following days. The rest of the host club notice she bears some distinct physical resemblance to Haruhi and to add to it, she's completely onboard with Tamaki's "romantic fantasies" they present to her, making them realize it's the "real-life version" of the imaginary Haruhi in Tamaki's mind. Tamaki however, states he doesn't think they're similar at all and shows no interest in her whatsoever.
In an early chapter, an author note states "I can't see Haruhi and Tamaki getting together." The second-to-last page of the entire series is of Haruhi and Tamaki on their wedding day, with an author note stating "Of course, I think the two will get married."
On a related note, a series that's an Affectionate Parody of shojo cliches ends up playing one of its biggest straight, that of the female main character ending up with the leading male.
Another related note. Early in the series Mori rejects a girl because he's too devoted to his master and cousin Honey. Later on he does end up marrying someone. Also the mangaka was originally planning on pairing up Haruhi with Mori.
Also, when Tamaki keeps referring to himself and Haruhi getting married after they've become a couple, Haruhi frantically reminds him that they're too young and marriage is far away in the future. However, jugding by the bonus page that actually shows them getting married they don't appear to have aged much, and if the online translation of the "Ghost Special" where they're all college students is to be trusted, Tamaki is referred to as Haruhi's husband there, meaning they waited no longer than two years. Awww.
The first host club member to get married is the most childish and spent the series running away from his responsibilities. To a previously unseen member of the Dark Magic Club whereas Honey is the living antithesis of darkness and the occult.
Bianca gets considerably less screentime than her game or anime counterparts. This ends up fleshing out her character more as well as making her more sympathetic as she laments over the fact that she really is a weak trainer who didn't accomplish much on her journey.
Giratina's Shadow Force would likely kill any ordinary human, but Diamond attempting to sacrifice his life on two separate occasions is actually what gives him immunity to it, allowing him to survive.
Homura gets slapped with this in Puella Magi Madoka Magica the Movie: Rebellion very cruelly. After spending over a decade rewinding time over and over in an attempt to save Madoka in the main series, she succeeds when Madoka becomes a god and is finally able to live happily. Then in the film, Homura turns into a witch thanks to the Incubators' interference and promptly tears her former friend down from godhood to steal her divine power, becoming Madoka's greatest enemy beyond anything that Homura had once tried to save her from in the process and conflicting with her once-sole motivation.
In Sailor Moon: Sailor Venus' character revolves heavily around romantic love, but the goddess Venus had nothing to do with love; she's more accurately a goddess of sex. Also Minako doesn't think she's pretty (at the beginning of her own manga), but Venus was a Proud Beauty. Minako also doesn't end up with anyone at the end of either manga despite both being anvilicious about her connection with it. The Dream and Stars arcs are also anvilicious about the Sailor Guardians and their duty. Duty (giri) is taken very seriously by the Japanese but not by other countries, including the countries where Classical Mythology has its origins. Also the main nine Guardians being Japanese when the gods are Greek/Italian.
During the S season, Sailor Uranus and Sailor Neptune are looking for people with certain Pure Hearts that possess the Talismans, knowing that whoever has them will die when they are taken. It turns out that Uranus and Neptune possess two of the Talismans. Neptune performs a Heroic Sacrifice to remove her Talisman and Uranus, distraught by her death, removes her own Talisman and gives them both to Usagi to protect.
Meta example: they already had their Talismans in the manga.
Mercury was the god of communication, but Sailor Mercury is shy and has trouble making friends. People often interpret her as a cold snob. The live-action makes her seem like she has an Ambiguous Disorder, possibly a "communication" one.
Despite claiming to fight for love and justice, Stars reveals that Usagi doesn't really mean the things she says. The whole time she's just been fighting for her family and friends, i.e. people she knows, not random strangers.
Relatedly, despite love (often solely referring to romantic love) being a central concept of the series (and a universal one at that) and this being a romance shojo manga, few of the main characters are in relationships by the end. Minako, Ami, and Rei in particular have their own issues with men. The end also beats the reader over the head with the very Japanese concept of giri.
Sailor Mars Does Not Like Men in the manga and Crystal. She's also the epitome of femininity and not very warlike. She's also religious, but follows Shintoism, not the religion of ancient Greece or Rome.
Neither Sailor Mars (war god) nor Jupiter (king of the gods) are Serenity's head bodyguard. That would be Venus, goddess of sex and beauty.
In School-Live!, in a flashback, Megumi is lectured that she is not cut out to be a teacher and is often called out by "tougher" characters like her mother and the Vice Principal. She turns out to be the best teacher the girls could hope for, having enough luck and common sense to survive the initial outbreak. She implements a scheme that preserves the girls' shaky sanity and she made the ultimate sacrifice to protect the children under her care.
Seraph of the End: The whole situation with the Guren/Shinya/Mahiru love triangle. To elaborate, Guren and Mahiru fell in love with each other at a young age, but they were violently separated because their social status didn't match. Eight years later, Shinya appears as Mahiru's chosen fiance, but she's still in love with Guren so he doesn't stand a chance. This is the part where you expect the two guys to fight over her for her love. Well, no. Mahiru is later revealed to have betrayed the Hiiragi family and involved with the Hyakuya Sect for rather.. disturbing actions that can harm the world. Guren and Shinya join forces in order to stop her and as they do so, Shinya finds himself gradually disliking Mahiru and falling for Guren instead. In the end, Mahiru becomes a demon inside Guren's sword, making him stop finding love again, but he doesn't seem to be bothered by Shinya's flirting toward him. And now Shinya is worried that Mahiru has taken Guren away from him. Yeah, it's both ironic and complicated.
Exa from Superior strictly abides by the rule of Thou Shalt Not Kill, yet his goal is to kill the demon queen that wiped out his home village (who, unbeknownst to him, is his traveling companion and Love Interest Sheila). To make it even more ironic, he ends up saving her life after finding out her identity.
Reiji wants to stop his Well-Intentioned Extremist father from fusing dimensions. His father has invaded other dimensions, used child soldiers, using propaganda to manipulate some of his own forces (as confirmed by Serena), and is willing to hurt dozens of people to get what he wants. Reiji's methods to stop him involve doing everything his father does, though on a much smaller scale. Reiji just believes that what he's doing is for the greater good.
Yuya is Fun Personified and his life's goal is to make people happy when they see his duels. Naturally, his Superpowered Evil Side traumatized several opponents and the audience, worries all of Yuya's friends, and leaves Yuya feeling terrible.
As a meta case, Yu-Gi-Oh! 5D's is frequently called the darkest incarnation of the franchise, while Yugioh Zexal is called the lightest. The Yuya-counterpart of the Synchro Dimension which is based on the former is a goofy Crouching Moron, Hidden Badass whereas the ZEXAL-based Xyz Dimension has its counterpart being a melancholic Knight in Sour Armour. Similarly, the villainous Yuya-counterpart of the Fusion Dimension which is based of Yu-Gi-Oh! GX duels and defeats duelists who are using monsters that Judai's friends own.
Odd-Eyes Pendulum Dragon is the Lighter and Softer counterpart to all preceeding protagonists' ace monsters and among the Four Heavenly Dragons. However, he gets the edgiest dark evolutions, and the hybrid form that resembles him the most is hinted to be his most evil hybrid form.
YuYu Hakusho: Yusuke spends most of the series fighting demons. Towards the end it's revealed he's part demon. Connected to this, it turns out Koenma's dad was evil all along and brainwashing demons so it could look like he was "saving" humans. The guy Yusuke was ultimately working for was the real villain and the demons he was hunting were innocent victims. Sensui hated demons, but ended up with one as a boyfriend. He also turns on the humans he had previously loved and protected and sides with the demons. His real plan is to die an ironic/karmic death by a powerful demon so he can atone for all the innocent ones he killed as Spirit Detective. Which leaves his demon boyfriend single.