Eren from Attack on Titan has no problems with headbutting Mikasa when she shows willingness to disobey her superiors' orders and later doesn't pull any punches while fighting the Female Titan he knows to be Annie.
In the third Rebuild of Evangelion movie, a situation arises where Shinji (male) Asuka (female) are forced to fight each other, both thinking that the fate of the world depends on their victory. After he's defeated her and her mecha running out of power prevents her from pursuing him further, she exclaims "You're the worst, you'd actually raise your hand against a girl!" Given that he was willing to talk and explain what he was doing and really agonized over having to hurt a former comrade, begging her to stop, and that she's the one who a) has actual combat experience and b) charged him from behind with a polearm without bothering to hear him out. One might wonder wether being male gave him any sort of advantage at all, especially since they were fighting with mechas, not their physical bodies.
Done without lampshading in Excel Saga. Il Palazzo shoots Excel with a pistol and a bazooka. This is a rare example of man-on-woman violence being (very) funny, perhaps because Excel herself doesn't make a big deal of it.
In Mobile Suit Gundam Wing, Dorothy Catalonia tries to InvokeWouldn't Hit a Girl against Heero Yuy during a fencing match. He quickly proves her wrong with a thrust that snaps his foil like a twig and embeds it in Dorothy's mask about an inch away from her face.
In Mobile Suit Gundam SEEDKira Yamato slugs Cagalli after she gets a bunch of her friends killed, and then tries to belt him when he calls her out on it. Muruta Azrael has no problems with slapping a girl (Flay) for not obeying his orders. Or shooting her a half-dozen times in the gut (Natarle). Neither does Rau Le Creuset, who kills Flay as well as others.
In Mobile Suit Gundam SEED Destiny, Kira ends of the being the one who kills Stella, though whether he was aware of her gender is up in the air. During the finale, neither Neo nor Athrun has a particular problem with tossing Lunamaria Hawke around like a ragdoll, and Anti-Villain Shinn Asuka makes a determined effort to kill Cagalli Yula Atha during their one fight.
Ikki does not care for his adversary's gender, and he is perfectly willing hitting his enemy is that person is a woman. It doesn't mean he's happy when someone else hits a girl in his vincinity, and specially if they're bystanders: he was pissed when Esmeralda was fatally struck down by Guilty, and later in the anime filler when little Helen, a 12-year-old girl, was tossed alive into a volcano by Agora and Shiva.
Boku No Hero Academia has Bakugou. This example is almost deconstructed in the his fight against Uraraka in the Sports Festival Arc. A lot of the audience boos him for being so okay with fighting a girl who seems so sweet and weak when compared to him, and his friends even call him out for it. Eraserhead though, says that it was a sign of respect, and Bakugou even states that there was nothing fragile about her.
On a lesser level, Tokoyami and Shigaraki are also this. Tokoyami fights against Yaoyorozu in the Sports Festival and is a pretty one sided battle to his side. Shigaraki, in his hatred for Dabi and Himiko, tried to kill both if not for Kurogiri interruption, he probably would have.
Basically every villain in the series has no qualms over fighting a girl, even less if they are heroes.
There is an instance in the anime where Yusuke reveals he holds this attitude, in contrast to Kuwabara, asking what gender has to do with fighting somebody who wants to fight and declaring there to be no purpose in treating an opponent differently because of their sex. The edited dub plays this straight, while the original Japanese/unedited dub implicitly averts by revealing that the demon Miyuki, the cause of this, is actually a Villainous Crossdresser transsexual, though Yusuke's precise dialogue could be taken as him telling Kuwabara the truth about Miyuki's gender only to keep him from starting a pointless brawl due to being so outraged over how.
There's even been a couple of times where he smacked Botan, once when she nearly blabbed everything about him being a Spirit Detective, and again much later after being mocked too much about his "Spirit Beast" Puu.
In this case, for every time he's hit Botan, there's three or four times Botan has hit him. And the receiver has usually done something to deserve it.
Monkey D. Luffy has a notable track record of this. As early as chapter two, he's attacking female pirate "Iron Mace" Alvida. In Whiskey Peak, he and Zoro give Miss Valentine and Mr. 5 an almost Offhand Backhand, and Luffy's the one who hits Valentine. In Alabasta, Luffy hits Vivi after Vivi gets angry at him for not wanting to run around pointlessly. In Amazon Lily, Luffy had to fight the Boa sisters, Sandersonia and Marigold and did so without holding back. He was also fully prepared to fight Hancock. He also recently told Big Mom that he would kick her ass when he gets to the New World.
Most members of the Straw Hat crew don't seem to have any problem with female opponents. Usopp in particular has fought against several female opponents, in one case only losing because Chivalrous Pervert Sanji stopped him from attacking. Zoro spent a large part of his childhood (unsuccessfully) trying to beat a girl, and even berated her for thinking that being a female made her any less capable a fighter. The only other member of the crew with reservations about fighting women is Chivalrous Pervert Sanji.
This was even used against an female opponent, Monet, during the Punk Hazard arc whom Zoro had to fight. She thought him not going all out against her meant he wasn't willing to fight a female. When Tashigi, a swordswoman who oddly looks like said childhood friend, berated him for this. He stepped aside and allowed Tashigi to fight her to show that she wasn't an easy opponent. Once his point had been made, he re-entered the fray by nicking Monet on the cheek and revealing to the both of that that yes while he doesn't like to fight females, it doesn't mean he won't, then proceeding unleash his killing intent and split Monet down the middle. Granted, he doesn't kill her (He didn't use Haki, so her snow powers weren't negated and kept her alive) but shows that if he was serious and Tashigi hadn't shown up, he would have. Monet, who had tried her hardest not to underestimate the Straw Hats, had a serious Oh Crap! moment when she realizes her initial diagnosis of Zoro was wrong.
Trunks destroys all of the future androids without mercy, killing Future Android 18 with an energy blast point-blank.
Super Buu couldn't care less about his opponent's gender; he turns Chichi into an egg and brutally crushes her, and also threatens to kill Videl when she provokes him. He does eventually turn Videl, Android 18, and Marron into chocolate and eats them alive.
Spopovich is not only very willing to fight Videl in a World Tournament, but he brutally beats her senseless. He would have killed her, but he is forced to simply knock her out of the ring in the end.
The antagonist of the movie Battle of Gods, Beerus, got slapped by Bulma. His response? Slap her back. Hard.
Naruto has no problem with this considering he challenged Tsunade to a fight after she insults the Hokage, and mocks his dream of becoming the Next Hokage. Granted, he doesn't manage to defeat her, but in their rematch he wins her over, and manages to get a kiss on the forehead from her, because she admits that his dream of becoming Hokage will eventually become reality.
Tobi also counts considering his fight with Konan, when he actually kills her at the end of it.
And then there's Neji, who almost kills Hinata during their fight after, with some help from Naruto, she shakes off his Breaking Speech and fights him back.
It's quicker to point out that Shikamaru is the only character in the entire series with reservations about fighting women, and he does it anyway. (Though he sometimes uses his shadow powers to have the girls hit themselves, like he does to Kin Tsuchi.)
Of course, it makes sense that this trope applies to almost every Naruto character. There are plenty of female ninja in the Narutoverse, so anybody that really Wouldn't Hit a Girl would probably get themselves killed (or fired) fairly quickly.
Sagara Sousuke from Full Metal Panic!. Being a Heroic Comedic SociopathCrazy Survivalist, he displays no reservations towards violence against women. Granted, he tends to prefer shooting at or bombing them instead of engaging in fist fights with them, but this appears to purely be his tactical preference more than anything else (seeing how he's rather physically underwhelming, and has the tendency to rely more on firearms instead of muscle). In one instance, he showed no hesitance in tackling Kaname's female teacher down a flight of stairs. And in another instance, he's shown to put a knife to the throat of an innocent old lady (though Kaname stopped him from doing anything).
Train Heartnet during the beginning of the Black Cat anime, while he was still emotionless and working for Chronos. Right in the beginning, he is shown beating down and assassinating a bunch of nuns (though...they apparently weren't actuallynuns, considering that they pulled out a bunch of guns and tried to kill him) during a mission.
Bandou, who proves himself an asshole by immediately back-handing a random female secretary for approaching him from behind, calling her a "stupid bitch" afterwards. In fact, the only people that the man has hit in the series are girls. He even lampshades it at one point, telling a girl that he is assaulting that he really doesn't give a crap whether she's a little girl or not. Though in the manga, he gets to deliver a Curb-Stomp Battle to a sadistic pedophile, rescuing Nana and Mayu. It's so hard to NOT like crazy old Bandou after he's done the Big Damn Heroes routine. That has to do with Mayu being Bandou's Morality Pet and the Unknown Man being pure evil. He may hit girls and all, but he won't rape or torture them.Hell yeah.
Kouta also does his fair share of slapping around any girls he thinks are unruly. In example, when he has a fight with a Yuka in Clingy Jealous Girl mode, he slaps her and then tells her that she's not being fair to him and others.
In one episode of Science Ninja Team Gatchaman, Ken punches a young girl in the stomach. He slaps her later in the same episode. In episode 40 he slaps Jun, the only female member of the superhero team.
In the Bamboo Blade manga, Toyama likes to Kick the Dog by beating up on new kendo club members, and Kirino mentions "Boys or girls, it doesn't matter to him. In fact, I think he picks on the girls even more." Of course, this makes the reader cheer that much harder when Tamaki beats his ass.
In episode 12, her patience with Louie reaches its breaking point when he comes back for her, after she had told him to go with the others. Which she took personally because it reminded her of the time when her former comrade, Hector, sacrificed himself by staying behind, when it should've been her. She assumed it was because she was a woman and accuses Louie of thinking the same thing. Louie gets up and hits back. At that point, the gloves come off and they duke it out (seen at 13:23-16:57, here).
Touma of A Certain Magical Index has no problem hitting women at all if their motivations involve the harming and murdering of decent human beings, and decks one female enemy (who was about to start a full scale war between Espers and Magicians that would result in the death of innocent millions) in the face at least twice in the same arc, knocking her out. In fact, almost nobody in the series has a problem with using extreme physical force against a female enemy, and to be fair the women in this series tend to be genuinely competent fighters that it would be downright stupid to hold back against. More than a few anime fans see this as a breath of fresh air.◊
From A Certain Magical Index-tan: Miracle of Endymion
Touma: "Ladylee or Shutaura? Which should I punch? They're both girls! But that doesn't matter! I believe in gender equality!"
The characters are prime examples, especially Alucard. Alucard does not hesitate to shoot Seras when she says that she is a virgin. However, the most notable example of this is the brutal murder of Rip Van Winkle: Alucard impales her on her own gun, drinks her blood, and finally absorbs her into his body. He also punches her in the face beforehand. In the TV series, Alucard kills a rogue female vampire without batting an eye. Additionally, he shoots Baobhan Sith to dispel her.
Jan Valentine intends on killing Integra when he and his brother storm the headquarters of the Hellsing Organization. He thinks nothing of it, and even claims that he may "skullfuck" Integra's corpse.
Hei of Darker Than Black is a consummate Combat Pragmatist and has no problem fighting female opponents. Veering into the villain version of this (he's a pretty ruthless Anti-Hero), on several occasions, when sufficiently angered, he has also struck defenseless female characters.
Despite widespread Fanon to the contrary, Ranma Saotome is quite willing to fight girls, though he does say once or twice that he doesn't like to do so and, for various reasons, goes easier on them then guys. For example, the whole mess with Shampoo started because he challenged her to a fight and then kicked her in the head off of the challenge log (and if he had been thinking to change back to his real form first, he wouldn't have gotten the Kiss of Death). He usually doesn't get to fight women particularly seriously because the matches he gets into opposing them tend to be goofy Martial Arts and Crafts stuff, and even if this contest involves physical combat he'd rather defeat them by ring-out or Defeat by Modesty than by actually hurting them. When push comes to shove, however, and the woman in question becomes a real threat to his or his friends' safety, he's perfectly willing to fight hand-to-hand with everything he's got —or bury them in a rock slide, whichever works.
Recurring opponent Pantyhose Taro outright says that he has no problem at all hitting girls. However, this means that he fights them exactly as he fights men —spending only as much energy and effort as necessary to defeat and subdue them. Therefore, after kidnapping Akane, he easily disarms and overpowers her with a few well-placed strikes; when fighting Rouge, he goes all-out, whether she's in her demure human form or in her psychotic Ashura form.
Fairy Tail characters in general seem not to see sex or gender as an obstacle to beating the crap out of people:
Occurs most notably when Psycho for Hire-turned-Sociopathic Hero Gajeel spends several gleeful minutes slapping a bound and helpless Lucy around just for the hell of it, but even then no one seems to care that Lucy is a girl so much as that she can't fight back.
Most of the characters don't have a problem hitting women. Yes, most of the heroes arewomen, but their enemies are happy to fight back, and the main (male) character doesn't flinch at beating up female villains.The one exception is Koutaro, who is a bit of a Technical Pacifist when it comes to women (he'll knock a female opponent out of the ring with the air pressure from his punch, but he won't actually hit her), but everyone else treats him like an idiot for making such a stupid lifestyle choice.
In chapter 317, Fate Averruncus is shown slapping a bound Nodoka (because she made him regret he didn't gag her as well)
Touta Konoe from Negima'sStealth Sequel, UQ Holder!, was taught by his adoptive mother that gender makes no difference on the battlefield.
For Guts in Berserk, there is no such thing as chivalry when he deals with female opponents. But then again, holding back against women like Rosine or Slan would be plain suicidal.
His first on-screen kill is a female demon after getting it on with her, sticking his Arm Cannon straight down her throat before blowing her brains out when she transforms to eat him alive like she previously did to Corkus during the Eclipse.
It is played straight during the early flashback arc. Future love interest Casca attacks him after finding out he had to strip her naked to treat her wounds, and he tells her that he'd knock her on her ass if she wasn't a woman. Of course, Casca's far less of a threat to him than demons, and it was more of a fit than a fight.
Kyon tried to punch Haruhi for going way too far in messing with Mikuru.
Agon of Eyeshield 21 has this as part of his establishing character moment. When Mamori turns down his advances he shoves her to the ground.
The world of Pokémon Adventures' has no gender issues as evil guys have no problem attacking heroic women and good guys have no problem attacking evil women. It helps that it's (usually) the Pokemon themselves that are doing the attacking, but it's worth noting that the girls take just as much damage as the guys.
Brock in the Pokémon anime actually hits Misty twice, and comically in the episode "Bulbasaur and the Hidden Village" when she's teasing him about having a crush on Melanie. She gets him back in the next episode, kicking him in the face after a fake bug scare.
Baccano!'s Claire Stanfield considers himself an equal rights activist: he fights for the right of people of all genders to have their asses kicked by Claire Stanfield.
Bleach: In general, the warriors of the Shinigami, Hollows and Quincies are all trained for battle and will fight both men and women. However, much of the time, male characters do struggle with the concept of fighting women and hold back in ways they wouldn't against male opponents.
Ichigo saves Kenpachi from the female Sternritters by throwing them into the nearby ruins. He lampshades the trope by commenting that he had thought it would be weird to fight girls, but now realises it's like any other fight.
Grimmjow is obsessed with testing the strength of his opponents, so he doesn't hesitate to challenge anyone who gets in his way. He stabs Rukia with his hand to see how strong she is. He ambushes Loly and Menoly when they are torturing Orihime, kicking Loly in the stomach, tearing her leg off while incinerating Menoly's upper body with a cero. When Orihime questions him in the middle of his and Ichigo's fight, Grimmjow grabs her in a Neck Lift and almost chokes her; he also threatens Nel with kicking her if she interferes.
Nnoitra believes no woman should stand higher than a man on the battlefield; his loathing for Nel begins from that point, and he disrespects Harribel as well. He is willing to cheat to defeat Nel. When he later encounters her child form, he doesn't hesitate to try and kill her. He also makes unpleasant suggestions to Ulquiorra, implying Ulquiorra should take advantage of his access to the imprisoned Orihime. Normally emotionless, Ulquiorra is disgusted.
In Yammy's first appearance, he smacks Orihime so hard he sends her flying, and then aims a cero at her and Yoruichi. When an arrancar nurse later restores his lost arm, he instantly kills her. He eventually attacks Loly and Menoly for no particular reason, first punching Menoly so hard she crashes through the wall and then beating Loly to near death.
When Jackie asks Renji if her gender is a problem for him, Renji tells her that gender doesn't matter on the battlefield as he thrashes her. However, he then refuses to finish her off because that would mean killing a defenceless female.
Ayumu of Is This a Zombie? will have no problem Chainsawing you to death if you mess with his friends.
For Shu's arc in Princess Jellyfish, he finally stands up to Inori after she keeps using blackmail against him. She then makes it look like she was Spurned into Suicide, which made him increasingly more worried. He very understandably gets upset with her when she reveals it was a morbid "joke".
While Tooru from Princess Princess is a Nice Guy for the most part, he makes it clear that he has his limits. In the finale, his Yandere cousin threatens to kill herself if he won't be with her. In response, he slaps her and yells at her for even considering such an option.
Okabe Rintaro of Steins;Gate punches an emotionally disturbed Moeka right in the face in episode 19.
More than a few cases involves women of all ages either being murder victims or getting hurt, whether they are Asshole Victims or not. Several cases stand out, one features a young girl named Minako got killed because she knew too much, as she found out that her 2 teachers were involved in a fraud and they strangled her to death to make it look like she committed suicide. Another case involves a man impersonating his dead friend and business partner stabbed his sister-in-law Machiko to death - though in this particular case it was self-defense, since Machiko tried to kill him so she could get her husband's insurance.
Dark Action Girl Grell Sutcliffe kills Madam Red when she refuses to harm Ciel, stating that she is "disappointed in her" for being so soft. She also writes Matilda's name down on her 'death list' for sleeping with Sebastian.
Alois also has few qualms with physically punishing his maid Hannah, even taking out her eye.
Being a World of Action Girls, the few male battle aliens in Sekirei have absolutely no issue with fighting women seriously. On the other hand, two different Jerkasses are also shown to consider hitting women for annoying them to be perfectly acceptable. Both get what's coming to them courtesy of Yukari and Shiina.
Nako's manipulative uncle in Poor Poor Lips, who strikes Ren in the face when she stands up for Nako, with the entire sequence framed like a scene of domestic abuse.
Almost every male in High School Dx D has no problem with hitting, slicing, stabbing, kicking them on the ground, or punching the girls through a wall or window. The hero Issei is usually quite content to spend time gawking at his female opponents, and has a technique designed to strip them (explicitly fueled by imagining them naked no less), but he won't hesitate to use his full strength against them when the chips are down.
Gintama. It's just not practical to treat the female characters differently than the male characters, mostly because they're just as powerful and crazy as everyone else in the world.
Yuuta from Love, Chunibyo & Other Delusions will give whoever he thinks deserves it a whack on the head, regardless of their gender. It should be noted though that while most of the people he hits are girls, when it's time for a guy (namely Isshiki) to get smacked around, Yuuta pulls out all the stops and just wails on him. Getting chopped or slapped on the head is nothing compared to being comboed.
In Bokurano, Jun Ushiro has a habit of hitting his sister Kana, which greatly disturbs the other Zearth pilots, especially Maki (who believes that he's using their being related as license to treat Kana that way, not knowing that they're not related). Kana's gender is less of an issue than her being younger than Jun, being his sister, and not doing anything to deserve it.
Almost played straight by Ryoma in the anime. At some point during the Jyousei arc, Ryoma is practisting his shots on his own; he then hears noises and sees that a local Alpha Bitch and her Girl Posse have not only pushed Ryoma's friend Sakuno to the ground, but are now threatening to do the same to Sakuno's best friend Tomoka. He then stops his practice and throws a tennis ball right at the Alpha Bitch so the group will stop harrassing the girls — had said Alpha Bitch not been fast enough to dodge, she would have been hit point blank.
In general, female duelists are always fair game for direct attacks, even by someone like Judai who states he Would Not Hit a Girl; exactly how much different hitting someone that way is from punching him depends on the situation and the interpretation. (It's clearly real in a Dark Duel, but whether the regular duels are Hard Light or simply work like some convincing rumble pack is debatable.)
In Yu-Gi-Oh! GX, the Gravekeeper's Chief strikes Assailant after she holds back in her attack against Judai; he seriously calls him out on this, and he replies with the equivalent of "mind your own business". (This was cut from the dub.)
In Yu-Gi-Oh! 5D's, the first clue to Rex Godwin's true nature was in the fourth episode; when Mikage told him Jack and Yusei were dueling, he got angry and started to strangle her. He calmed down and let go after she squeaked out a frightened apology. (Again, this was cut from the dub.)
Jack Atlas punched Barbara after she tried to hold two children hostage and threatened to kill them. He commented that anyone who would try something like that does not deserve chivalry.
Inuyasha himself fights female villains such as Kagura and Tsubaki just as seriously as he does any male foe. When he fought Princess Abi, he explicitly mentioned that he doesn't like fighting women, but Abi is such an evil bitch that he's making an exception with her.
Naraku certainly doesn't discriminate against hurting and killing women. He himself was directly responsible for Kikyo's death.
Played for Drama early in the Wandering Son manga. Takatsuki is a closeted trans boy and he got into a fight with a boy in his elementary school. The boys mother is especially mad at her son for getting into a fight with a girl. The mother saying this upsets Takatsuki.
In the second episode of the Explorer Woman Ray OVAs, the hired hands of bad guy Rieg Vader are not afraid of dealing with the heroine and her teenage girl sidekicks (all of whom give better than they get). Their leader on the other hand is ashamed of such behaviour and tells his men off. Rieg himself tries to pull a sword on Ray when she sabotages his plans.