Papa Wolf/Fan Works

"There was no way for the overwhelming wrath of God to be made evident through mere behavior. The archangel was no longer responding to the demon's mocking himself for the light that surrounded his already blinding form had no place on the conceptualized wavelength of mortal comprehension; it was the response of an incensed Father to the torture and ridicule of one of his sons, it was the vengeful mark of the Lord Himself."
 * Skinner, Nemo, and Jekyll all have a tendency in this direction in The Private Diary of Elizabeth Quatermain. Jekyll has (eventually) his adopted son, Nemo has his foster daughter, and Skinner has both his niece and his love interest.
 * Tony Stark becomes this to his adopted son Harry in the Harry Potter/Iron Man crossover fanfic Harry Potterandthe Invincible Technomage. It is also demonstrated that many of the heroes feel this way toward their allies' children.
 * In Supernatural's Deterioration of Reason, OC!Gabriel was already shown to be a protective big brother over Castiel and his Berserk Button is if any harm comes to Castiel. But when the demon Belial, who had kidnapped and tortured Castiel, implied that he did something else to Castiel, not only does Gabriel go into Tranquil Fury, but it's revealed that God Himself has had enough.

""You took my little brother, tied him up, pumped him full of heroin, and left him to die in this shit hole. Now I ask you: do you think I have the slightest bit of remorse about cutting you open and letting your guts decorate the floor?""
 * From Batman fic Antidote for the Poison, Jason Todd in a rare moment of brotherly concern is furious when he finds out that some drug dealer had injected Tim Drake with a dangerous amount of heroin as an attack against Batman.

"The Warden: Uh oh..."
 * In the Lord of the Rings fanfic Ancient Prophecy fullfilled, one of the Valar (the gods without Capital G) slew the children of their Guardians. Understandably the Guardians in question weren't so thrilled. They battled the Fourteen Valar, destroyed the city they dwelled in and still inspire such fear that the Valar have to call upon the  Big Bad to aid them!
 * Spyro from The Legend of Spyro a New Dawn is pretty protective of his adopted egg, just like Cynder, but a much bigger Papa Wolf is Ember's father, Blaze. When the Warden has Ember overpowered in their battle, Blaze blasts him, despite the Warden's collar inflicting debilitating pain on any of the cursed slaves who attacks or touches him in anyway. Once, Blaze tears through the cage holding him and an entire mob of Warrior Gargoyles to get his claws in the Warden.

""You do understand that if you ever, ever again strike a student in so brutal a fashion, you will not survive the night, correct?""
 * AU Devil May Cry fic "Like Father, Like Son" has Dante exhibiting his demonically-protective side when he finds his son Nero injured courtesy of a police officer with temper problems, and when Nero is later threatened by members of the mafia. The second time Nero gets threatened by the son of a mafia head, a partial Devil Trigger sends the man leaving with tail between legs. And when Dante finds the demon Baul, who had all but put Nero near Death's door... Cue Unstoppable Rage and Roaring Rampage of Revenge with a dash of There Is No Kill Like Overkill.
 * In Harry's New Home, Snape will go to any lengths to protect his ward Harry, even if it included breaking rules or facing the Dark Lord and Dumbledore (if necessary) to do it. For that matter, Dumbledore does not like seeing any of his students harmed in any way, especially if it's Harry. His Berserk Button was pressed when he found out Umbridge used a Blood Quill on Harry and in the prequel, he gave a casual warning to Snape who earlier in a fit of rage slapped Harry. All in a cheerful tone and a benign smile.


 * One Piece's Muzzled shows a moment where Zoro literally resorts to biting Marines (after having his swords taken away and his hands tied) who tried to separate him and the kidnapped Usopp and Nami to trap Luffy.
 * In Supernatural's Crossing the Line, John Winchester kills a human being for the first time because
 * In the Ultimate Re Imaginings, Clint is this towards Joey as once nearly killed the boy's actual father for putting him in the hospital and breaking his arm when Joey had been twelve.