The werewolf soldier, Vinnie from Skins. He rips open another monster's throat in a flashback scene during a prison fight and he's not much more than a teenager at the time. The first time we see him in the main story arc, he's hunting another werewolf soldier and in the next scene, he's shown holding the other soldier's severed head.Implying he tore it off with his bare hands!
Oh, she's no nanny ... she's a killing machine whom Klaus Wulfenbach repurposed into a babysitter. Threaten her kids and she will rip you to shreds.
Even the Baron's secretary and Gil's valet get in on it. (Okay, the former is a Sparkishly-altered minion with enhanced strength and dexterity, and an extra set of hands, while the later is actually a British spy posing as a valet, but still. Badass.)
Captain Tagon has demonstrated his ability to handily defeat both Schlock and an anthropomorphous elephant in close combat. He once took a knife away from an enemy by catching it with his eye. Then he pulled it out and used it to kill the person who threw it.
All of Tagon's Toughs earn their name. And then there's Petey...
Take a look at what the paladin O-Chul does in ThisOrder of the Stick strip and tell me that he's not badass. This is apparently a regular occurrence for him, and yes, that is an acid-breathing shark. Based on the number of attacks/round he gets in a strip, he is at least level 16, a higher level than at least one of the PCs. Word of God claims he has a constitution score in the mid 20s, when most characters would be lucky to get their primary stats into the low 20s without falling into Crippling Over Specialization .
O-Chul does not have a Constitution score, Constitution has an O-Chul score!
The titular character of The Adventures of Dr. McNinja, who took out evil Ronald [=McDonald=] with a mime ninja rocket launcher, punched out a giant crazed lumberjack, captured and now rides a trained velociraptor, beat up Death himself, and recently punched Dracula in the face.
Gordito, Dr. McNinja's sidekick, as well. A tween who grew a massive mustache through sheer force of will, he killed a clone of Ben Franklin's Zombie, killed several flying magical sharks of doom summoned by a ghost wizard, and proved he was more cunning and quick-thinking than the woman who trained both the Good Doctor and Gordito himself when he saved her son from Dracula's last minute cheap shot aimed at him. Oh, and when he was first informed of his new status as sidekick, this is what he had to say:
Gordito:"I don't kick. I shoot people. That makes them die."
And Dan McNinja, the hero's father- The moment that his mustache was revealed, hordes of ninjas bowed down to him in homage, crowning him their leader. He escaped an attack of ninja drug abusing teenagers — he lit himself on fire. Because if you're on fire, ninjas cannot catch you.
Do not mess with The Mother McNinja. Trust us. Just don't.
Miranda Deegan is an archmage with a nigh-infinite knowledge of arcane magic; Donovan Deegan is an awesome musician and master swordsman; Dominic has incredible intellect, an amazing ability to think several steps ahead, and has never thrown a single punch throughout the length of the comic; the Deegan family is turning into a Badass Family... And Luna is marrying in to the family!
The MS Paint Adventures series Problem Sleuth has the titular hard-boiled detective, who is unique from his teammates in that he does all of his own asskicking throughout the story instead of creating replicas of himself. His fighting technique, "Sleuth Diplomacy" runsontheBadasseryofthecharacter. This is the guy who saves the entire imaginary world and defeats the Final Boss DMK once and for all through sheer virtue of his charisma alone. He's the series' version of Kamina.
The Midnight Crew from the Intermission. They take on a rival gang of Time Masters that outnumbers them four to one on their home turf and nearly succeed in killing them all with nothing but an arsenal of relatively mundane weapons and prior knowledge of their foes' powers.
There should definitely be more people from Homestuck on this list. Practically everyone has their own badass moments. Of the Beta kids, you've got Jade, now a Reality Warper who came up with a flawless plan to get the Beta kids through to the Alpha kids universe, Rose, who took on Jack while Grimdark and held her own even before she Godtiered, Dave, mentioned above, and John, who now has such control over his godtier powers he can turn into wind itself and outrun Green-Sun powered Grimbark Jade, for God's sake. And that's just the kids!
Richard is an all-powerful warlock who performs henious acts of evil out of nothing more than boredom. If he doesn't have acess to his magic he can still kick your ass with his bare hands, because he drained the soul of a monk once (it tasted like chocolate).
Dexter. He scaled the enemy base, fought the Big Bad with giant robot hands, and ,just because he's that awesome, slapped the Big Bad across his face after he broke the nearly unbreakable glass tube his girlfriend was in.