Batman: The Animated Series: Again, Batman's one principle is to never take a life, but if you dare to enslave innocent children to steal for you like The Sewer King did, you better damn well pray that he does hold onto it.
Batman: I don't pass sentence. That's for the courts. But this time, this time, I am sorely tempted to do the job myself.
In "Over The Edge", we see justhowfar Commander Gordon will go out for Batman if Barbara is ever killed in the line of bat-duty.
Batman's reaction in the infamous flashback in Batman Beyond: Return of the Joker... when he was beating the heck out of The Joker after the latter revealed that, he not only kidnapped, but subjected Tim-Drake!Robin to three weeks of electrocution-based torture as well as truth serum, and then turned him into a grotesque miniature version of the Joker. He even states "I'll break you in two!" in a very chilling manner.
At this point though, the Joker is so desensitized to Batman's menacing threats that he isn't intimidated even in the slightest. (It's not until the 2nd Batman calls the Joker out on being a pathetic loser with an absurd fixation on the orginal Batman that Joker starts getting upset).
Aaahh!!! Real Monsters had The Gromble act this way towards his students (especially if they were being bullied for something they didn't deserve) and genuinely seems to care about their education and is willing to implement 'tough love' if he thinks their ego needs to be knocked down a peg or two. Though when push comes to shove you can guarantee that If anyone dares try to harm or endanger his students he'll be there to defend them. As he demonstrated when he punished a parasite who invaded Oblina's body, defended Ickis to the other students when his spontaneous combustion made him into a social pariah and where he berated a scientist who called his top student, Oblina a 'subject' instead of his 'student.'
Also Slickis deserves mention as he saved his son, Ickis' life at the risk of his own against a giant tank.
The only thing Scrooge McDuck loves more than money are his three little Nephews Huey Duey and Louie. If you thought he is a dangerous Badass Grandpa when he is pursuing treasure, whoa boy you have not seen how terrifying he can be if you hurt one feather on their heads...
Well, there had to be a reason that Donald entrusted them to Scrooge... this is that reason.
And when Elisa was shot in her apartment (accidentally by Broadway), Goliath tore through the city to get the gangster he believed did this. When he did find the gangster Tony Dracon, he was willing to kill the guy right then and there for what he (supposedly) did to Elisa.
In American Dragon Jake Long the dragon trait skipped a generation, so Jake's mother can't protect him from the supernatural threats he encounters — instead it's Jake's grandfather who does so. Never mind that he even stands up to the Dark Dragon's minions when his entire family is threatened... and obliterates them single-handedly.
Jake's dad OTOH, despite being an ordinary human, gets a couple good moments. He manages to save his son from some kind of winged, moose thing during a camping trip, and later saves him again from a bunch of vampires.
Charles Ofdensen, the band manager in Metalocalypse, is seen by some fans to be the Papa Wolf of metal band Dethklok. He is extremely protective, preparing and executing elaborate security measures and counter attacks for their concert in the first season finale; going against assassins twice his size in hand-to-hand combat; having Rockzo the clown beaten and tortured on two occasions for being a bad influence on the youngest member of the band; and warning another manager attempting to take over his position that he would have to kill him to keep him away from the band. And then killing that man himself.In a swordfight.
To drive that point even further, the villain was his own brother, Orm. And Aquaman didn't give a single thought about kicking his ass and letting him die.
King of the Hill: Hank Hill. Whether it's a Jerkass boss putting Bobby in danger at his job, or a Jerkass football coach abusing Bobby and his teammates after losing, they quickly learn the hard way just how dangerous an angry Hank can be. One would think they'd know not to mess with someone who's so into propane. And propane accessories. (Otherwise, though, Hank is something of a "Well Done, Son" Guy.)
Thug:"I thought that old guy inside was your daddy." Bobby:"No, no! This is my daddy! This one right here, the one with the golf club!"
Dale, too, even after learning that Joseph is "part-alien."
To elaborate on Dale, he once heard his son screaming in his sleep. What does he do? He kicks the door to his bedroom open, brandishing two pistols, ready to blast the threat to kingdom come. When Joseph says he just had a bad dream, Dale says, "Oh. How about I read you a story?"
In The Fairly Oddparents, even a Man ChildBumbling Dad like Mr. Turner is capable of fighting with teeth and paws to defend Timmy. Just watch the episode where Timmy wishes he could merge with dad's Cool Car, then Vicky steals the car and he believes Timmy is stuck in it...
Both of Timmy's parents, despite being comically irresponsible enough to leave him with an evil babysitter, have gone to crazy lengths to protect Timmy. This came to the fore when Timmy wishes they had superpowers, and he ends up using this to his advantage when convincing them to give up their powers.
Don't forget the end of the Fairly Oddparents movie, where Papa Wolf dad and Mama Bear...mom double-team Mr. Crocker for abusing their son. Much ass kicking ensues.
Actually, Mr. Turner technically could be counted as a literal "Papa Bear" at that point.
In case you don't get the joke, Mr. Turner had recently had his hands turned into bear's claws after saying he'd tear someone apart with his bare hands
Tom and Jerry: We all know Jerry Mouse is no push-over in regards to Tom the Cat. But if Tom ever lays a paw on Nibbles/Tuffy, the local Heartwarming Orphan and Jerry's adoptive pup, he's in for even more of a pain in the tail than usual. Nibbles/Tuffy's introductory episode leaves the deal very clear; Tom spanks the little mouse and, after releasing himself from a trap and checking on the other's well-being, Jerry lets out an enraged lion's roar and brutally beats up Tom.
You also don't mess with the local neighborhood bulldog Spike's son, Tyke, in any fashion, though that really should be obvious.
Tom and Jerry to each other; they are the only ones allowed to chase, attack and beat each other like they do. Do not try and harm one of them... as the other will make you regret it.
Agent Six in Generator Rex is this to Rex. Heck, just watch him in "What Lies Beneath" or his fight with White Knight.
Even Peter Griffin on Family Guy is capable of this now and then (even if the rest of the time he is an outright Abusive Parent). An episode centered around him becoming more protective of Meg after she almost drowned in a flood, even going so far as to smash stuck-up Connie d'Amico's face into a glass surface until it was a bloody pulp for making fun of her. In another episode, Stewie gets nabbed by Disney World employees who force him to sing for the customers, and Peter manages to save him and outrun a dangerous security guard. Stewie even hugs him for it at the end.
And in the episode when Meg dates Quagmire, he gets really suspicious and angrily asks Quagmire if he slept with Meg.
American Dad! also does this. "Surro-Gate" is a good example, as it shows a Camp Gay who previously solved fights with dance moves out of West Side Story punching out Stan in one hit after he kidnaps the guy's daughter.
Stan: That's not campy. That's not campy at all.
Stan despite his Jerkass tendencies certainly has traits of this with his children as well, should we ever forget what he did to his own boss for insulting Hayley.
Private of The Penguins of Madagascar has shown this. When the penguins are tasked with taking care of an egg in shifts, Private is so horrified by the other penguins' rough handling that he steals the egg away and snaps at Skipper.
The Venture Bros.: Brock Samson is the Alpha Papa Wolf whenever someone threatens the Venture family. See Victor. Echo. November. for the naked, murderous evidence.
Dr. Orpheus as well to his own daughter and towards the Venture boys.
TaleSpin: Though obviously not shown to the same extent as Rebecca, Baloo has traits of this around Molly as well (likely to further emphasize his chemistry with the former). Whether she's been kidnapped by bandits, zapped by a microscopic ray, or just wants her Christmas wish to come true, Baloo is pretty insistent she come out of it all with a smile on her face.
And God help you if you screw with Kit. Baloo's protective instincts come out even more heavily when he's involved.
Dr. Doofenshmirtz of Phineas and Ferb may be an incompetent villain, but don't even try to hit on his underage daughter unless you want to quickly be teleported to another, monster-filled dimension.
Perry the Platypus, especially when it comes to Phineas and Ferb. There was one time when Friendly Enemy Doofenshmirtz indirectly threatened Phineas and Ferb with his latest scheme, Perry quickly beat him up, handcuffed him, and called for backup all within ten seconds.
Happens again in the movie Across the Second Dimension. Perry didn't break his masquerade even when a robot punched him across the room. But when the robot was ordered to do the same thing to Phineas and Ferb, he immediately jumped up and punched the robot just as hard.
God help you if you try and kill Perry when Doofenshmirtz is around (and vice versa) for he will go nuts at you; he is the only one allowed to kill Perry. Likewise, for Perry, he is the only enemy Doofenshmirtz is allowed to have. Got that Peter the Panda?
The Powerpuff Girls usually don't need Professor Utonium to protect them, but the rare times they do, he definately qualifies. (Or at least he tries.)
The cartoon version of Beetlejuice is typically an easy-going prankster whose main interest is driving the rest of the Neitherworld crazy. But on those rare occasions when Lydia is in serious danger, Beetlejuice will show just how he got the title of Ghost With The Most. Insulting or humiliating Lydia is also a bad idea, as Claire Brewster found out the hard way on more than one occasion.
The Ren & Stimpy Show ... In "A Visit To Anthony," Ren and Stimpy are severely intimidated by Anthony's father. And they have every reason to be. He's very large, heavily muscled, despite his age, and unlike most of the "lummoxes" seen in the show, he is not only healthy-looking, but reasonably intelligent. Just getting a threatening speech from him puts the fear of god into you. His silent rage is even more frightening when coupled with his weeping when he thinks his son is in danger, even if it's just of being disappointed.
The Simpsons: In the episode "Simple Simpson," Homer Simpson sees the Rich Texan making Lisa cry. He then throws a pie in his face. He would have beat the man, but he was told he'd go to jail if he committed another assault.
He has gone great lengths for his children despite how people think of him as a Jerk Ass, like when Maggie was having trouble finding easter eggs, and trying to help Bart with his homework and Lisa become popular.
Hakoda also has some signs of this. Even though Katara is a very powerful Waterbender and Sokka becomes a great warrior, he will stay behind and be captured by the Fire Nation in order to let them escape. There is also his reaction to Katara's announcement that someone was threatening Kya in "The Southern Raiders." When he hears his wife is in danger, it is obvious that if that Fire Nation sailor doesn't haul his ass out of there double time, he will find out just why the Water Tribe hasn't been overthrown yet.
YMMV on that particular scene, as we don't see much of a reaction. Everything else between Hakoda and his kids certainly suggest he counts.
Fire Lord Azulon could be seen as a much darker version of this to his older son, Iroh. When his younger son Ozai tries to usurp Iroh's right in succession, Azulon is so enraged he orders Ozai's innocent son Zuko be executed to teach Ozai a lesson. Fortunately, Zuko had a Mama Bear of his own to prevent this.
Even Avatar Roku is shown looking out for a certain troubled great-grandson of his. At the Fire Temple, Aang channels his spirit to pwn the evil Fire Sages, Zhao, and his soldiers... and then Roku melts the chains holding the good guys and Zuko, letting them all escape before he destroys the temple.
Tenzin in the Sequel SeriesThe Legend of Korra is definitely this. In the season finale, Amon threatens to take away his children's bending. When Tenzin gets loose, he sends Amon flying off the stage.
Ratchet from Transformers Animated doesn't like to hear his friend Omega Supreme, who he mentored during the war, being threatened. Of course, Omega is a Person of Mass Destruction built to end the Great War, so this doesn't happen often, but...
Ratchet (to the Autobot High Council): Omega Supreme is one of us. An Autobot. A friend. Harm one circuit on him and you'll answer to me.
It should be mentioned for the un-initiated, that Ratchet is both an old man and a medic, with no offensively designed equipment. Yet you still don't doubt that he could very well hand them their asses on a plate if pressed.
Speaking of that franchise, in Transformers Prime, there's Optimus. Go after Jack, Miko and Raf at your own risk.
Then there's both Bulkhead and Bumblebee, towards Miko and Raf respectively. Jack has Arcee.
In Code Lyoko, while his ability to actually make offensive moves was very limited, Franz Hopper tried his hardest to protect Aelita to the best of his ability. In fact, that was a key part of XANA's plan through much of the fourth season; he directed William to capture Aelita and hurl her into the Digital Sea because he knew Hopper would rescue his daughter, forcing him to reveal himself and leave him open to an ambush by XANA's forces.
Teenage Mutant Ninja Turtles: Master Splinter made sure that his adopted sons could take care of themselves, but if you happen to be planning on experimenting on them, you'd better pray he doesn't find out.
The 2003 series might be the strongest example, as circumstances caused Splinter to be in combat situations a fair bit in that series. Fair bit of advice to that continuity: if you're beating on, or even just FIGHTING, the Turtles and you hear a gravelly voice growl "MY SONS!", just give up now. It'll be less painful for you.
Somewhat off-screen in Winx Club and crossing with Mama Bear is Oritel (Bloom's Dad). After both he and his wife think both their daughters to be dead, they according to one account went completly berserk at the ones responsible; the Ancestral Witches. Considering how high they are in among other's Faragonda's and even Valtor's regard, that says something about the power which was unleashed. Ouch. When Oritel has returned by Magical Adventure, he is fiercely protective of Bloom, banishes Sky from Domino when he thinks Sky has dumped Bloom, and doesn't hesitate to fight the Trix and Ancestral Witches when they threaten Bloom.
To explain what happened in that movie: when the Trix attacked the Winx he jumped out of nowhere and, after promising the Ancient Witches he'd make them pay for killing his older daughter, proceeded to kick the Trix' asses single-handly in spite of having no magical power and his sword having been depowered alongside all the fairies; and when the fairies and his sword recovered their power the Ancient Witches-possessed Trix (who were easily defeating Bloom and the Winx Club) could barely cringe in fear when they saw him charge before he turned the side of the battle (it was the Winx to wipe out the Ancient Witches for good, but they would have lost without Oritel kicking their ass while they prepared the spell). It's also stated in both movies that it was Oritel and his wife Marion to destroy the Ancient Witches Coven one by one in revenge for the apparent deaths of both their daughters, with the Company of Light being there mainly to cover their backs and finish stragglers, and when they were finished the Three Ancient Witches were weak and bodyless, most of the coven had been wiped out, and of the two survivors Mandragora had been imprisoned with the Ancient Witches, and Valtor (the Big Bad of season 3, with the power to defeat the rest of the Company of Light alone) had been left barely alive and survived only because they were in a hurry to finish the Ancient Witches.
The Smurfs: You don't threaten Papa Smurf's little Smurfs unless you want to be on the receiving end of one of Papa Smurf's potions.
Grouchy towards Baby Smurf. If Baby Smurf's introductory episode wasn't any indication, in one episode it was revealed that Grouchy couldn't swim, followed by the other Smurfs trying unsuccessfully to teach him. But the moment Grouchy saw Baby in trouble, all fears left him and he immediately dived into the water to rescue him.
When Egon of The Real Ghostbusters was literally paralyzed with fear by the Boogey Man, he found the strength to escape his bonds when the Boogey Men threatened the Junior Ghost Busters, a trio of children he had been mentoring.
Ben 10 may be well able to protect himself thanks to the Omnitrix, but on one occasion, his father ended up attacking a High Breed with a BFG for threatening him. Considering how powerful the High Breed had been up to that point, doing that is pretty dang impressive. Ben's grandpa Max has also shown traits of this.
And Ben grows up into one in at least one timeline. Kevin 11,000 hurts Ben's son Ken. Cue Ben going Way Big and pummeling Kevin into the ground in an Unstoppable Rage.
Rath, the badass Crazy AwesomeLarge Ham extraordinaire became this in his debut. After warming up to a Triffin Prince that's supposed to help end a war, he finds out that the prince ends the war by being eaten. Rath didn't take this kindly ("Eating babies is NOT! COOL!")—he jumped into the mouth of the alien who ate the prince and came back out the same way, threatening to knit a sweater out of the alien's organs should he declare war. It worked.
SpongeBob SquarePants: Spongebob of all people has this for his pet snail Gary. He's only stood up to his boss Mr. Krabs on a few occasions, one of which involved him not being himself at the time and two others being him being pushed over the edge by a great deal of abuse the entire episode. However, on one occasion, Krabs used Gary to steal money for him thanks to him somehow being a living change magnet, something that Spongebob had already told Krabs hurts Gary. When Spongebob finds out, he instantly chews Krabs out for it without a second thought. On another occasion, Spongebob became the adopted father of a bunch of baby worms and this part of him awakened once again. He tackled Larry (the strongest guy in town) when he tried to eat them, then disabled a truck by tearing the engine block out of it with his bare hands to stop it from running over them. Also manages an inversion in one episode when his criminal cousin Blackjack apparently kidnapped his parents, overcoming his crippling childhood fear of Blackjack to confront him. Turns out he hadn't kidnapped them but it still counts.
Ant-Man II from The Avengers: Earth's Mightiest Heroes mainly uses his powers and abilities to ensure the safety and well-being of his young daughter. In the episode in which he officially became the new Ant-Man, he punished Crossfire for kidnapping her by kicking him in the face, then covering him in ants.
Primarily inverted in Godzilla: The Series, where Godzilla, Jr. will go to crazy lengths to protect his adopted father Nick Tatopoulos.
But also played straight with Nick. If you are human and you do something that harms Godzilla, Jr., Nick will end you.
Buck Tuddrussel in Time Squad. While known to be a complete Jerkass at the worst of times, and often lets Otto get hurt through blind negligence; Tuddrussel will kick some major ass if Otto is in mortal danger and the thought of losing him to someone else makes him just as pissed. Same goes for the campy robot partner Larry, which crosses into Mama Bear territory.
Hugh Test in Johnny Test. Normally a bumbling dad obsessed over meatloaf, he is extremely protective of his kids, even confronting a wrestler more than three times his size to ensure their safety.
Octus/Newton is this to Lance and Ilana in Sym-Bionic Titan. Bonus points in that he pretends to be their father when they're at home.
Mike Chilton acts as this towards his True Companions, the Burners in Motorcity. First noticable in "The Duke of Detroit" episode.
The Zeta Project shows us the DCAU is filled with these. Agent Bennett, the closest thing the series has to a villain, a man who has dropped everything to chase a criminal across the country, promptly drops everything to save his son. He even works with said criminal to get his son back and spends time with him afterwards rather than go back to work. He's very dedicated to the NSA, but touch his kids and he just doesn't give a crap about them.
Young Justice: Black Manta towards his son Aqualad, despite almost killing him in season 1, in Season 2 he responds to Sportsmaster's request to kill him with an angry "No one touches my son." After that, he tries to have Psimon, and later Miss Martian help him. When Sportsmaster and Cheshire attack his sub, he orders his men to help his son instead of him, and later abandons his fight to save him. In addition, when his men set a charge to blow through a door and rescue him, he detonates it prematurely, blowing the soldiers away, wanting to get to his son as soon as possible.
In the Teen Titans episode "Betrothed", Galfore, Starfire's k'norfka (guardian) is introduced, a huge, hulking, muscular guy who is willing to use violence if someone does anything that even might be a theat towards his ward. (Oddly enough, this is one thing that Beast Boy learns rather quickly.)
Being this protective to one's ward may be a common trait for a k'norfka, actually. Starfire herself becomes a Mama Bear towards Silkie after she gives herself this title towards him.
In the Adventure Time episode "Simon and Marcy", Simon went to extra-ordinary lengths to protect young Marceline even when she had a cold by trying to find some Chicken Soup. He was determined to protect her (at the cost of worsening his already unstable mental condition) by putting on the crown and using his powers to freeze the threats (or in one case knock out a mutant with his crown and another with a pillow). Needless to say it's not a good idea to harm Marcy when she's with Simon, because as demonstrated in the episode he would do anything to protect her.
Mr. Bogus, of all people, actually shows shades of this, in regards to watching over his younger cousin, Brattus. If you even dare to pester or threaten Brattus, then may God have mercy on your soul!
Two examples on the heroes' side in The Amazing Spiez. Cal Clark, the main team's biological dad and Jerry (carrying over from Totally Spies!). Messing with any of the Clark kids when either of these men could find out is a bad idea.
Captain Planet and the Planeteers: Yes, Eco-Villians, by all means, try to kill the five kids who are, more or less, the adopted children of an immortal Earth spirit. Granted, it's implied that Captain Planet can't kill, but if you dare mess with his Planeteers, you'd better RUN when he shows up.