Takeshi Kovacs. This is a man who will happily torture-murder (permanently) anyone whom he has judged to be a bad person. Or merely for getting in his way. Or for having the wrong religious convictions. Kovach has endured subjective months in simulation being mutilated whilst inhabiting a female body. What did he do when he escaped? He calmly strolled through the facility perma-killing everyone he saw, and coolly strutted out the front door with a head wrapped in a jacket.
The founder of the 00-program and that their leaders codename M originated with him,
Sherlock, the show that translated the mythos to the 21th century, choose to portray Mycroft as a man that had full control of the CCTV-network (of London, which is the largest and most dense in the world,) a man who was asked by Sherlock to "try not to start any wars tonight", and who asked Sherlock to relocate a stolen Goverment Flashdrive with a street-value of £600.000.000 since he was busy elsewhere. So this Fanon is alive and well.
Not to mention he's played by a writer for the series, so he quite literally has control over what goes on in the show.
Meaning that he's so badass that the fourth wall isn't enough to stop him.
Sir Nigel from Sir Arthur Conan Doyle's The White Company is so unstoppable he defeated a bear with a handkerchief
If you threaten his friends and family, he'll necromance a city and then go after you. Or become The Lancer for a god or fallen angel.
Attack his girlfriend? He'll kill your species.
He uses heavyweight faeries as calculators and donut fetchers.
Attack him in an elevator? He'll crush you with the elevator while he's still in it.
He kills Faerie nobles and Queens simply because they're in his way (or worse, messing with his date)
He punches gods in order to be friends.
He broke off a piece of a fallen angel's soul, and then made that piece cry just by talking to it.
He tries to bill God Almighty for freelance work through Uriel, God's wetworks man.
He frightens an Eldritch Horror that feeds on fear. It's like drowning a fish - it's not clear how that's even possible.
Harry is a living weapon against the Outsiders. It took the entire White Court hours to subdue one, Harry has beaten two of their champions by himself. Each in minutes. One when he was a teenager. Outsiders come from outside reality and eat magic. Like Harry Blackstone Copperfield Dresden gives a fuck.
In universe example: Voldemort can kill you with his eyes.
Dolohov considered this by the fandom, going so far as to claim the Dolohov defeated in the final book was his son, who was immediately disowned.
Kingsley Shacklebolt also gets the 'facts' treatment.
An example of an in-universe actual meme: although it isn't mentioned explicitly, Merlin was evidently a really, really prominent one in the wizarding world. He got so memetic that nowadays wizards swear in his name, and the highest honor that can be given to a person is the Order of Merlin (although Neville may have changed that; see the Real Life tab.)
Yaxley became one after Deathly Hallows Part 1. He doesn't chase you. He walks after you and still gets you.
Samwise Gamgee from Lord of the Rings. It helps that he bested the insectoid spawn of an Eldritch Abomination and stormed a castle full of Orcs, overawing the survivors with his presence alone and leaving rumors of a grim Elvish lord.
Orcs in general. They iz made for fighting and winning. And singing (about eating you.)
When Baba Yaga crossed over from Russian fairy tales into Western fiction she went from an old witch frequently bested by little boys and flocks of swans to the most powerful magician in the world, able to stand up to gods themselves.
People will line up to almost certain death instead of risking Commander Vimes using sarcasm on them. Also see the quote on Heroic Willpower about him.
When he was sent away as a diplomat in The Fifth Elephant, the Ankh-Morpork City Watch was left in absolute chaos with an incompetent leader. Despite this, the crime rate of the city decreased. Why? Because Vimes won't be away forever. And when he returns, he will not be happy. "And when Commander Vimes is unhappy, he tends to spread it around with a big shovel."
Nobby Nobbs once declined being crowned king of Ankh-Morpork because Vimes would 'go spare'.
The Assassin's Guild lost so many members trying to claim the bounty on his head that they officially declared him off-limits. Vetinari is the only other person to hold that "honor". Plus, Vimes made his house so Assassin-proof that it's now used as an obstacle course to test overconfident apprentice Assassins.
Vetinari's snark is even more feared than Vimes's. And rightly so.
Moreover, Vetinari's reputation for nigh-invincibility among fans is such that you'd never guess that he lost the only hands-on fight we've seen him engage in since his student days. (Granted, he was taken by surprise and was up against Mr. Tulip, who in terms of physical combat—and art appreciation—may be well a Badeverything.) His true Badassedness rests in his ability to turn any sort of conflict into a verbal one, at which he is the Snark Codifier.
Likewise, Granny Weatherwax's Badass status, in Witches Abroad, is such that even the narrator dismisses the possibility that she might've been shaken up by seeing her long-lost, long-hated sister Lily in a mirror. Even though that's exactly how she's behaving!
Lu-Tze of the History Monks is an in-universe example. He's so famous that when an acolyte at the History Temple knocks over his shrine thinking it's only a sweeper's, he spends the rest of his life as a sweeper hoping to make up for it. Not to mention that even though he's not technically a monk, he has more access to the temple than anyone but the Abbot himself, and has the personification of Time as an apprentice.
The entire Ankh-Morpork legal profession trembles in abject terror if the senior lawyer Mr. Slant so much as glances crossly in their direction. The fact that Slant happens to be a zombie has absolutely nothing to do with this, except insofar as it's given him more time to get dangerously good at his job and to gather dirt on everyone else.
Cthulhu. Seriously, Lovecraft had an awful lot of bizarre and seriously freaky cosmic horrors. Cthulhu appears in all of one story (though, like most of Lovecraft's Great Old Ones gets name dropped in countless others) and isn't nearly as terribly outlandishly freaky compared to the others (it's roughly humanoid, after all) and is escaped by a man who turns his boat around and steers towards it. Nonetheless, Cthulhu has become the icon of the whole Cthulhu Mythos and a memetic symbol for all that is evil.
On a related note, Nyaralathotep has become renown for being being a pants shittingly terrifying ultimate combination of Troll meets Humanoid Abomination, regardless of incarnation.
In-universe: Major ________ de Coverley in Catch-22. Everyone is too scared to ask his first name. He was able to bring an end to a loyalty oath clusterfuck with two words. Then again, those words were "Gimme eat", so...
Inspector Javert in Les Misérables, who takes down a gang of armed and vicious thugs by walking into the room (the fourteen officers with him wait outside until he calls it clear). He also knows he's following Valjean, even though Valjean is dead.
JeanValjean is a massively powerful man, who was turned from his bitterness in a single act of kindness. After this, he becomes probably the nicest guy around, even to the point where he lets Javert live, even though the guy has made his life a living hell on countless occasions. Even with this niceness, he is lethally intent on protecting those he loves, specifically his adopted daughter. Points for the fact that despite his obvious capability and justification to do so, he never kills anybody.
Among fans of The Wheel of Time, Bela. Bela is ta'veren, Bela is the Creator, Bela is a Darkfriend, or Bela will kill the Dark One. For the uninformed, Bela is a horse. Not a Cool Horse, but a damned reliable one.
Randyll Tarly, the Jerk Ass father of Samwell Tarly, was selected by the ASOIAF fandom as their answer to Chuck Norris Facts. Threads are dedicated to coming up with series-ralted facts for him, such as "When Randyll Tarly weds a Frey girl, the musicians kill themselves!" (though of course you'd have to have read the series to get the jokes.) He has a Valyrian steel greatswordnamedHeartsbane. He is noted in series, by characters who see through burnished reputations, as being one of the greatest soldiers in the realm, and unlike more of the other examples on this page, being named as a Memetic Badass is not a compliment.
Petyr Baelish has developed a more serious memetic badass reputation amongst the fandom due to the character's success in bending a continent to his desires. Some fans think he can achieve just about anything.
Jaime Lannister, an in-story memetic badass of the series, also became a fandom memetic badass in Suvudu.com's "cage matches." The site pit 32 fictional characters against each other in one-on-one fights to the finish. Due to reader votes, Jaime Lannister defeated Hermione Granger, Cthulhu, Temeraire, and Kvothe in spite of being so obviously overmatched due being an otherwise normal human lacking any magical ability and his sword hand. Rising backlash over his success ultimately caused him to lose to Rand al'Thor in the final round, though George R. R. Martin did pen a very good short story on how he believes the duel should go, which manages to pay tribute to his late friend's work as well as examine the fundamental differences in their worlds.
In-universe, Tywin Lannister is one. Everyone is so scared of him that a single verse of The Rains of Castamere (a song about the torments he inflicted on a vassal who dared to consider rebelling) will put an end to any opposition.
The Longknife family of the Kris Longknife series are another in-universe example - at least, the ones that are considered "one of those Longknifes" - not totally a good thing, as many people would prefer to avoid associating with them.
He's also an in-universe example, especially since he's the antithesis of the Empire's "strength over smarts" philosophy, scaring the hell out of the New Republic.
In the Hand of Thrawn duology, the scheme to use a Thrawn impostor to take over the Empire works in part because the mere idea of Thrawn having somehow survived his assassination and coming back for another go freaks people out.
Thrawn's second-in-command and successor Gilad Pellaeon also has this reputation. He's a Badass Normal—no Jedi powers, no Mandalorian training, no crazy alien strategy powers—and yet he kept the Imperial remnant together, more or less on his own, for approximately fifteen years. That's nearly as long as the Emperor's reign. He even (somewhat) overcame the Jedi Mind Trick of Joruus C'Baoth.
Pellaeon's resumé: Served as the Admiral on the ship Anakin Skywalker was stationed on. Was the nominal second in command of the fleet at Endor (in the event of Vader's flagship, Executor, being destroyed), and turned the rout into a well-ordered retreat. Managed to salvage most of Thrawn's fleet, then took over the Imperial Remnant after the last petty warlord fled in disgrace. Pushed back the Yuuzhan Vong from the galaxy, then combined the New Republic and the Imperial Remnant into one Galactic Alliance. Supreme Commander of the GA's armed forces until he was assassinated in an attack by the Sith Jacen Solo, where the entire fleet he was traveling in was attacked as as distraction for his assassination. It still only barely worked.
Kal Skirata. He convinced clones programmed with obedience to defect. And then he stole billions of credits from the Republic. Oh yeah, and Hutts owe him favors.
Time Scout: An in-universe example. Sven Bailey is widely recognized as the most deadly individual on TT-86, which makes him one of the deadliest individuals alive.
Paul is so badass that he has been deified by his followers.
Fremen in general are pure badass. Sardaukar win against any ten or so normal house guards. Fremen wipe the floor with Sardaukar. Even in the sequels, where Fremen undergo a serious downgrade due to better living conditions, there is still no-one who can take even a single one on.
Duncan Idaho was so badass he earned everyone's respect and then was resurrected endlessly for at least the next five-thousand years.
Leto II was badass enough to actually become a Sandworm. You know, that monster that is cameod in every game that has a desert level. The only thing that could kill him was water. According to his own plan. It could even be argued that Leto II is more Badass than Paul, since he accepted the Golden Path whereas his father was terrified by it.
Danny, hero of John Steinbeck's Tortilla Flat, becomes one of these in-universe by going out with a bang immediately after throwing the greatest party Tortilla Flat ever knew.
From Fablehaven, Patton Burgess. We learn he actually did almost everything he's known for and deliberately kept a number of them secret.
The 'titled' pilots in Stone King are in-universe examples. Subverted in that while all are at least competent titan pilots, none of them are anywhere near as Badass as they are generally believed to be.
Rachel from Animorphs. She will morph into an elephant and STOMP YOU FLAT!
Song at Dawn Alienor is so widely known as an Iron Lady that there are in-universe ballads of her leading an army of amazon in battle against the muslims.
The Book of Mormon: To members of the LDS church, Captain Moroni. In one of his first appearances he is described in this way: "If all men had been, and were, and ever would be, like unto Moroni, behold, the very powers of hell would have been shaken forever; yea, the devil would never have power over the hearts of the children of men" (Alma 48:17). He then spends the next twelve or so chapters proving it.
Begbie of Trainspotting. Deconstructed Trope: His mates build a mythos around him about what a psychopathic badass he is. This causes him to believe his own hype, and makes his immoral behaviour even worse.
Kindling Ashes: In-universe example-Baltair is amused to hear that tales of his exploits have grown wild in his absence. He can tear down castle towers with his claws and burn entire military companies with a single breath of fire!
The Weed of Crime bears bitter fruit. The Shadow never fails.