The OYAJI, from the manga of the same name, is a bloody extreme example of this. We dare you.....No, we DOUBLE DARE you to lay a finger on anyone in his family!
The last time two yakuza members tried to burn his family alive, their whole gang ended up being massacred in the most brutal way possible and then burnt to ash! The scary part? This was done right in their own base by the old man with a shovel all lone!
Heck! Even his would-be son-in-law learned this in a very,verypainful way!
Kenzo Kabuto from Mazinger Z and Great Mazinger. It is arguable if he wasor was nota good father. It is not arguable when his older biological son was about of being killed he sent a Humongous Mecha after the people was attacking him, and when his adoptive son was about of being killed, he blew his assailant and himself up. Therefore, althought his parental skills left much to be desired, you DON´T try to hurt his sons.
Danbei Makiba from UFO Robo Grendizer. If he thinks you are going to hurt his daughter, he WILL hang you with his bare hands. Or shoot your brains out (the only reason Kouji and Duke are alive is because his aim is awful). If he entrusts you to drive his daughter somewhere he'll load his shotgun in front of you as he warns she BETTER does not get harm in any way, shape or form.
Henry Maaka from Karin is usually a weak-willed wuss, but when his daughter Karin is in trouble, he will literally let himself burn to rescue her from the hospital people who think she's an Ill Girl, but could potentially discover that she's a vampire.
Most people try to kill vampires with stakes. Henry uses uprooted trees.
Takahata is this way as well, but to Asuna in particular he's an adoptive father. Although only because his self esteem is too low to be her boyfriend.
It is implied at first, then outright stated, that Nagi and later Negi saved the world because it was the only way to save Asuna.
Oga from Beelzebub seems to not care for Beel, but, if you put a finger on the baby...
In chapter 107 he openly declares himself to be Beel's parent, emphasizing this trope even more.
Bleach : When Nnoitra threatens Yachiru. Yachiru claims Kenpachi would be mad if she was threatened, but Kenpachi barely bats an eyelid over the claim. However, when Nnoitra actually attempts to kill Yachiru rather than just threatening to do so, Kenpachi leaps into action.
In the second sequel series Yu-Gi-Oh! 5Ds, Crow goes on a Roaring Rampage of Revenge when he returns after the appearance of the Dark Signers' evil fog to find out the kids he's taken in have all vanished.
Also Jeager (to an extent). You may not be able to tell when you meet him, but he'll do anything for his son. (In one episode, when he and his family were down on his luck, he went hungry in order to feed his wife and son, telling them he'd "already eaten". Unfortunately, he's a Bad Liar.)
Napolean from Yu-Gi-Oh! GX is an interesting case. He wants to be his son Martin's protector, but he can't; as a teacher at Duel Academy, showing favoritism towards a student is a professional taboo, so he's forced to isolate himself from Martin (one of the hardest things he ever did, as he put it). As fate would have it, Martin becomes the victim of Demonic Possession, courtesy of Yubel, at which point Napolean pleads with Judai to help him.
Also, Hakkai. Don't threaten or hurt his comrades. JustDON'T!
Whenever he learns that his daughter Ran Mouri and/or his charge Conan Edogawa are or have been in danger, Detective Conan's KogoroMouri is definitely not pleased. And you do NOT want to provoke a man who looks and acts like a slob, yet is a National-level judoka andacts at his most competent when It's Personal. More than one suspect has been at the receiving end of a powerful judo throw for this.
Inspector Juzo Megure is also very protective of the kids who hang out with Mouri and of his own subordinates. Better shown when he goes It's Personal mode in a case involving young women being attacked: he refuses to let Action Girl Satou act as a decoy once his Berserk Button was pressed, and later took a metal pipe to his head while protecting Sonoko from the culprit. It's explained that this comes from one of his first cases, where he failed to protect a schoolgirl posing as a decoy and she almost died. Fortunately, the girl got better... and then they gotHappily Married.
While there are many Papa Wolves and Mama Bears among the Sympathetic Murderers, there was a specially dark take on this trope during a two-part anime only episode. A businessman had contacted Kogoro to locate an assassin whom he had hired to kill him, having backed off the deal but not being able to find him and tell him so. It turned out that he was using Kogoro and others in a Batman Gambit destined to find and kill said hitman with his own hands, since one of his assassinations jobs led to the accidental death of the tycoon's beloved daughter. Conan had to beg the grieving and very pissed off father to not exact said revenge, but he also made sure that the hitman's threat was neutralised and he was taken into custody.
Dragon Ball and its sequels have a lot of dads, but the grand master of this trope is Piccolo, to the point where his constant and epically badass rescues of his pupil Gohan become something of a Running Gag.
Despite wanting nothing to do with Future Trunks (usually ignoring him or just pushing him aside whenever Trunks tried to reach out to him), Vegeta went crazy after Cell killed Trunks.
"How could I let this happen to my son? He has sacrificed everything for me and I have done nothing but ignore him. I won’t give up on him! There is still time to change things. Cell has crossed me for the last time! He has tricked me in battle, mocked my Saiyan ancestry, but this! This time he has gone too far! He will pay the ultimate price for what he has done to my son!"
The Non-Serial MovieBojack Unbound has Goku, despite being dead, attacking Big Bad Bojack for trying to Bear Hug Gohan to death. And he succeeded, giving Gohan the encouragement and strength he needed to win.
Throughout the movie, Vegeta appeared to have lost his passion for fighting since Goku died, not even watching the competition. But when Trunks was in danger, he immediately sensed something was wrong and headed to the battlefield, making a Big Damn Heroes moment to help Trunks out of a tight spot.
An old man in the episode "Free the Future", while Android 18 was blowing things up after getting angered with Android 17 for killing a boy she thought was cute, attempted to shoot Android 17 (as that boy was in fact his son). It failed, because Android 17 was resistant to gunfire, and needed saving by the time Trunks arrived.
This is also inverted, as there's a common theme throughout the show where whenever Goku or Piccolo is in immediate, life-threatening peril, Gohan snaps and proceeds to kick the bad guy around until the latter stops moving.
Yusuke from YuYu Hakusho is a subtle example. Harming/killing at least one of his loved ones gets mad, but if it's Keiko or Kuwabara, he will kick their ass!
The best example comes from the battle against Suzaku, who was stronger than Yusuke, capable of creating six clones of himself (all strong as the original) and, once he clones himself, has to be killed alongside all his clones, because leaving just one barely alive will only lead to him absorb the rest, heal himself and summon six clones. Obviously Yusuke was having a lot of trouble, but as soon as Suzaku treathened Keiko he killed six of the Suzakus (including the original) and greviously wounded the seventh. At that point Yusuke was exhausted, but the survivor had absorbed the others to heal and cloned himself again... At which point Yusuke used the power of his own soul (a move that nearly killed him) to recover the strength, and overpowered and killed all the Suzakus at once.
One Piece has Captain Whitebeard, formerly one of the four most powerful pirates in the world. An attack on one of the Whitebeard Pirates is never forgiven and his reactions are legendary-when the World Government sentenced his adoptive son and lieutenant Ace to death, everyone involved knew immediately that it was effectively an outright declaration of war.
After Ace's death, instead of going insane with rage like most had expected, Whitebeard in a frightful and calm way defeated his very powerful murderer Akainu in two blows and, in the same blow, split the entire Marine island in half... despite being stabbed, blown up, gutted and with half his face burnt off. All to avenge poor Ace's death. And you thought Whitebeard on a rampage was bad?
Shanks, when Luffy is threatened. There is a reason why he lost that arm of his...
Luffy himself is a version of this trope, as any attack on the physical or emotional well-being of his crewmembers is taken personally and likely to result in an angry and violent beatdown, like he did when Nami had a hertbreaking Heroic BSOD once her efforts to save her village were thwarted by her Bad Boss and he epically beat up and defeated said boss. Prior to the Time Skip, however, he was just a fledgling, made clear from the fact that he wasn't quite strong enough to back up this fierce protective instinct yet. He found that out the hard way in Shabaody, where the entire crew was more or less beaten half to death and scattered to the four corners of the Earth by Bartholomew Kuma and he was helpless to stop it. But especially, considering the fact that Kuma was on their side, that was nothing compared to when he went to The Alcatraz and then the World Government's headquarters to rescue his older brother from execution, only to have him die in his arms. Seriously, if he hadn't had Jinbe there to knock some sense into him, he wouldn't have been able to Take A Level In Badass to transcend pretty much all the limitations he had, and then some.
Zoro too. He's normally not the type to take revenge. But Ohm made him reconsider that when he set traps that brutally injured Chopper. Also, when Robin was almost killed by Enel, he caught her before she fell (despite his earlier distrust against her) and furiously attacked Enel as a result. In fact, any member of the Straw Hats will beat up anyone who dares to hurt their True Companions, as proven when the Franky Family beat up Usopp, and the remaining male members returned the favour and destroyed their house in retaliation.
Garp is a Grandpa Wolf who would have killed Akainu for killing Ace if Sengoku, the Fleet Admiral, hadn't stopped him. He even tells Sengoku to keep him down or he would have tore Akainu to pieces.
Also, Luffy's actual father Dragon the Revolutionary has appeared only once or twice, but one of these apparitions puts him squarely here. When Luffy was about to be arrested by Smoker...Dragon shows up and keeps him from using his weapon. Then a gust of green wind blows through the island, freeing Luffy from Smoker's clutches. It hasn't yet been revealed if the wind was Dragon's doing, but...
Smoker himself acts as a Papa Wolf to his subordinates, especially Tashigi. He doesn't hesitate jumping in to save Tashigi and his men from Trafalgar Law telling them to run away and taking him on his own. Also he was really worried and shocked about his men when they get caught in a huge explosion. Then, when he finds out Vergo attacked them, he lays a beat down on him, and allows himself to lose their battle, in order to get Law back his heart, who has major issues with Vergo from the past. In short, you do not screw with the men under Smoker "The White Hunter", or you will regret it.
Kenshin, however, manages to reconstruct the trope and play it straight. When he fell through the Despair Event Horizon due to believing that his girlfriend Kaoru had been massacred by Enishi and his group, what brought him back to his senses was Yahiko's girlfriend Tsubame telling him that Yahiko was fighting Enishi's group alone. Few later, Kenshin pulls a massive Big Damn Heroes to save Yahiko.
Fullmetal Alchemist: "Don't EVER mock my son." Screw with Hohenheim's kids and you're in trouble. Not only that, but he's willing to sacrifice his own life to bring his youngest son Al back from the Gate, and when asked by Ed why would he do such a thing, he calmly replies, "Because I'm your father".
Maes Hughes also counts, telling several party-going toddlers not to "try anything" with his daughter. Complete with Scary Shiny Glasses and Dramatic Gun Cock. It's Played for Laughs, but you know that if anyone ever really did threaten his beloved Elicia, there'd be hell to pay.
There's an interesting straight use and subversion of this trope, pulled off by the same character (a villain). He's the leader of a wolf-themed gang, and one of their raiding parties gets their asses handed to them by Kenshiro. When he finds the bodies, he howls for vengeance, taking the rest of the pack with him to hunt for Kenshiro. The subversion comes from the fact that when they are utterly defeated by Kenshiro and Rei, one of the midgets in his gang comes up to him and asks for help. He tells him to get lost, that he can start a new pack anytime he wants. Then they all die.
In the second OAV based on the video game Fatal Fury, titled FATAL FURY 2: THE NEW BATTLE, lead hero/fighter Terry "The Wolf" Bogard has lost his will to fight and live after being beaten by Wolfgang Krauser, only to have a street kid named Tony tag along with him. Tony, who lost his father in a street fight and works as a shoe shine-boy to support his mom Elsa, worships Terry's reputation as a fighter and wants to be his disciple. After the defeat, Terry spends half the special getting drunk and not caring about anything... It is only after Axel Hawk, the heavyweight boxing champion of the world, orders his sparring partner to beat Tony within an inch of his life in a bar (after Terry drunkenly refused to fight Hawk when challenged), does Terry rise out of his funk...and drops Hawk with ONE PUNCH. Even Hawk can't believe it (as his inner narration mentions).
In The Movie, Kim Kaphwan gets to show off his Papa Wolf credentials as well. When a Brainwashed and Crazy Cheng Sinzan steps into a party he's attending with the main cast and his family, Kim offers to fight him so his two kids can see him kick ass. His rival, however, soon starts wiping the floor with him, so much that Joe has to be stopped by Andy from breaking in... but the very moment one of the Kim boys begs his daddy to not lose, Kim brings himself back and completely curb stomps his enemy with a single Ho-oh Kyaku.
Tendo Soun of Ranma ˝ isn't as Bad Ass as most of the cast, but disrespect any of his three little girls and you'll realize that he hasn't forgotten much of Happosai's Training from Hell. Saotome Genma, on the other hand, is cursed to transform into a literal "Papa (panda) bear". See the opening statement on why this trope is named "Papa Wolf" and not "Papa Bear" and you'll understand the Fanon that Jusenkyo curses are Personality Powers.
Kurogane is like this. Though he has an initially calm attitude when Seishiro "kills" Syaoran in Oto, you can just tell there's the hint of death in his dialogue and in his face. Though it's hard to tell if he's more mad about Syaoran's "death" or Fai's. Either way, don't mess with anybody in his party.
Sesshoumaru from InuYasha usually doesn't get too excited about much. Threaten Rin, though, and a beatdown like none other will commence. The best example comes from the manga... when Rin is taken to the underworld by a hellhound, Sesshoumaru follows and kills it. When she is already dead, whoops the King of Hell's ass to get her back. When this doesn't work, he actually shows the closest thing to human emotion he's ever done in the series, purifies the souls of the dead as an afterthought, then rips a hole back into normal reality. After all of this, his youkai queen mother acknowledges this and uses her powers to resurrect Rin since Sesshoumaru, of all people, is clearly unhappy about her death. He goes from Aloof Big Brother to a combination of John Creasy, Jesus, and Spawn in a Crowning Moment of Awesome and Crowning Moment of Heartwarming unparalleled in the other 500+ chapters of the manga.
Despite being the hero of Lone Wolf and Cub, Ogami Itto averts this trope - if anything he's an Underprotective Dad. Mainly because his toddler son Daigoro is a samurai too, and though he he does love his kid... if he should be killed, that's a risk that comes with the job.
However, Ogami has pulled more than one You Shall Not Pass for his clients either in the process of getting the job done or to repay a debt of honor: once, he stopped by a village whose men had all been drafted for war and helped them till a field, even to the point of cutting down anyone who tried to pull him away, because he'd been asked to do so by his last assassination target.
Despite being the youngest (male) of the group, Mobile Suit Gundam 00's Setsuna F. Seiei is quite the Papa Wolf for his teammates in season two. This is so pronounced that sensing his comrades all on the brink of death pissed him off to the point that he unknowingly initiates the "Trans-AM burst mode", completely turning the tide of the battle.
An ironic example is Sergei Smirnov, who has been called ''Papa Bear'' (because in-universe he's nicknamed "the Wild Bear of Russia") by fans with the description of Papa Wolf in mind. He did fit the Papa Bear description given above regarding his treatment of his son Andrei, but with Soma Peries he was Papa Bear all the way.
Black Lagoon's Ginji Matsuzaki. Do not even look at his protégé Yukio wrong, or this Bad Ass swordsman will cut you down. Ask about what he did to Chaka, to start...
Rokuro Okajima aka Rock. As seen with Gretel, Garcia, and later, Yukio, he'll go to great lengths to shelter children and teenagers from harm. Kidnapping and then molesting and abusing Yukio is a good way to make this usually mild-mannered, diplomatic and well-spoken former Salaryman angry enough to actually cuss you out and physically assault you.
Fairy Tail: You can do anything to him, even completely destroy his guild and Makarov will only get irritated, but if you hurt any of his guild members, there's a very good chance he will make you stop breathing.
Don't so much as think of threatening Pinoko or Black Jack will cut you to ribbons. Then sew you back up. Then charge you everything you're worth for the trouble... Yeah, it's just that kind of story.
Also, when a child's life is in danger, expect Black Jack to work even harder for the kid's sake. Or to deal even harrsher gambits in an attempt to make others empathize with said kid.
While not a biological father, Sousou/Cao Cao from Ikki Tousen is this towards his friends. So much, that his Superpowered Evil Side took full control of him whenever he saw them in danger. It first happened with his Unlucky Childhood Friend Chuukou (he thought the bullies at their judo club were attempting to rape her), and later with his Bash Brother Kakouton (who lost his eye while shielding him)). And in the anime series, he also recruited Myousai by protecting her from a rapist and offering her a chance to be his subordinate and fighter instead of a Child Soldier.
They may have marital problems in Macross 7, but don't ever think of threatening any of their children or their city or their ship; coz when Mama Bear Milia and Papa Wolf Max Jenius team up, you are definitely screwed. Especially emphasized on their killer combo attack in Super Robot Wars Alpha 3 as seen here.
Minato Namikaze aka the Fourth Hokage from Naruto. In fact, the whole deal with the Kyuubi has just recently been revealed as the struggle between him and Tobi, with Tobi using Minato's love for his wife/partner Kushina (then-host of the Nine-tailed fox) and their newborn son Naruto (future host of the same Fox) for his advantage. And we already knowhow THAT ended...
Hizashi Hyuga deserves a mention here, as the mere realization that his son Neji is a member of the Branch Family sends him into a murderous rage (which is stopped before it can begin courtesy of Hiashi activating his curse seal - and doing so is the first step in causing Neji to spend at least nine years of his life afterward as the inversion of this trope!)
Also Hiashi for killing that Cloud ninja for attempting to kidnap Hinata.
Gesicht: Even if the world ends, I won't let you go.
One of the weirdest (andthat'ssayingitNICELY) examples ever is Dr. Shingen Kishitani from Durarara!!. In the novels, we learn that Shingen was the one who cut Celty's head off and sold Saika's sword off to the Sonoharas... but he did it in order to protect his young son Shinra from Namie Yagiri's grandfather, who threatened to kill Shinra if he didn't.
Black Cat. Have some nefarious scheme for Eve? Want to study the nanomachines that she uses? Feeling compelled to dissect her just because you can? Pray to the god of every religion you've ever known that Train and Sven don't find out about it. Especially the former of the two.
In Fruits Basket, we have Kazuma Sohma, foster father to Kyo Sohma. In one chapter of the manga, Kazuma proclaims his intent to protect Kyo single-handedly from the entire Sohma family if he must.
There's also a sketch in one of the later volumes, where Kazuma meets with Kyo's Jerkass of a father, cheerfully telling him that now that the Zodiac curse has been broken and Kyo is free, it's time they had a little talk about Kyo's future. Kyo's father looks like he's pissing himself in fear. It's Played for Laughs, but given the psychological abuse the father heaped on Kyo (at one point he accuses Kyo of trying to kill him for standing too close to him), it's very much a Crowning Moment of Awesome.
Not even a freaking typhoon could stop Kenzan Takakura from getting medical attention for his ill daughter Himari. And he still had enough pluck to shield one of his sons, Kanba, from a falling lamp. And had his other son Shouma been there, he would've protect the kid too.
In Happy Yarou Wedding, Yuuhi is very much one. Because his own childhood was so lonely he wants to give Shouta the best childhood he can and is fiercely protective over him.
Kotetsu T. Kaburagi of Tiger & Bunny may have a strained relationship with his daughter, Kaede, due to his job as a superhero (which she isn't aware of) meaning that he has to spend a lot of time away from home, but he's not about to let anything harm his little girl. This is showcased when he lifts a collapsed tree to save Kaede from a collapsing shrine even when his powers run out, and later, when Maverick has a gun to Kaede's head, Kotetsu reveals himself to be Not Quite Dead and punches Maverick in the face.
James of Pokémon fame is rather protective of his Pokémon in the Sinnoh arc, especially Mime Jr. (which is a baby Pokemon, by the way). Sometimes he goes as far as teaming up with Ash and company just to keep them safe. Oh, and when Jessie and Meowth refused to help out one of those times, he attacked them.
Ash himself counts too. Countless times, he has put his life on the line without hesitation to save his Pokemon. And for that matter, Ash's Pokemon can be fiercely protective of their owner... Just ask his Grovyle, who had been Brought Down to Normal due to an Heroic BSOD, but recovered his powers out of sheer willpower upon seeing Ash in lethal danger!
In the fifth movie, Latios is a Brother Wolf to Latias. He refuses to let any strangers into their secret garden, and is even willing to sacrifice his life just so his sister and the town of Alto Mare could be safe.
The titular Onizuka from Great Teacher Onizuka who goes through great lengths to protect his students. In fact, you don't even have to be his student. He will rescue you anyways. This includes getting shot multiple times in an attempt to rescue a school girl (who happened to be trying to discredit him as a teacher) he saw being kidnapped while on his way to take an exam.
Sai Nanohara from Jubei Chan is almost always a Bumbling Dad, but once he learns that his daughter Jiyu is the reincarnation and Soul Jar of Yagyu Jubei, he decides to not stay aside and does what he can to help her. In fact, his first Papa Wolf act was calling out Yagyu Jubei himself upon his treatment of Jiyu. To Jubei's very face. And in the Grand Finale of the first season, Sai also manages to give Jiyu/Jubei a Cooldown Hug to dispossess her from Jubei's influence, putting himself at great risk to do so.
Kenichi: The Mightiest Disciple gives us a number of examples. The most prominent ones are Hayato Furinji, who's a Grandpa Wolf for his biological granddaughter Miu and also for Kenichi to a degree; Sakaki Shio and Apachai Hopachai, two of the Ryozanpakou masters who train Kenichi and will go all-out to protect him if he's in serious trouble; and most recently the Big Bad himself, Saiga Furinji, who joined Kenichi's group in disguise to rescue the kidnapped Miu, his daughter.
Not to mention Kenichi's father, Mototsugu Shirahima, who, when he found out just how brutal Kenichi's training was, tried to escape with Kenichi from the masters. He even tried to save his son from a boulder that was rocketing towards them, regardless how futile it was.
Guts from Berserk acts like this toward the Cute Witch Schierke, and toward his True Companions in general. Ironically, he doesn't act too much like this toward his insinuated son, the mysterious Moonchild, but most likely because Casca won't let Guts near the little boy or because whenever the Child does appear, larger than normal battle shit happens and they never spend any "quality" time together. However, when the latter happens, the roles get switched.
Daikichi from Bunny Drop makes for a realistic example, by adopting a 6 year old no one wanted to take responsibility for, and doing whatever it takes just to make sure she gets a decent childhood. Commander Badass would be proud.
In the Street Fighter IV OAV The Ties that Bind, none other than Ken Masters becomes this. With good reason: his wife Eliza has been abducted by Crimson Viper, and then he learns that she's pregnant. This is so awesome from his part that Viper herself notes that the massive fighting power he displayed was no slouch compared with none other than Ryu's Satsui no Hado. (And might as well be the Power of Nothingness that opposes said SNH); considering how cheerful and cocky the dude is, it puts on perspective how fucking pissed off he was.
He's the first person to stand by her as she's being rejected by the society for her telepathy. The word society includes his daughter Kumiko, or Haruka's mother. In fact, he disowned Kumiko as the latter disowned Haruka, and when he comes across her again some 10 years later, the first thing out of his mouth is a warning that he never wanted to see her again. The two only reconciled as Kumiko and Haruka reconcile.
When he first meets Moritani in episode 6, he implies quite clearly that he knows what she did to Harukanote She asked thugs to attack Haruka's Understanding Boyfriend Manabe, which indirectly broke Haruka out of Hope Is Scary. and that she isn't off the hook with him.
Pretty much all of the adults in Soul Eater act this way. Justified, as Spirit really is Maka's father and Sid adopted Black*Star as a child after his entire clan was destroyed.