Arguably Batman himself! Arkham Batman is probably the strongest Batman incarnation of all time. In the first game, Batman: Arkham Asylum, he was injected with Scarecrow's toxin multiple times and fought through it with no rest or antidote. In the second game, Batman: Arkham City, he can punch Mr. Freeze's suit with his bare hands....and hurt Mr. Freeze. In the prequel, Batman: Arkham Origins, he defeated Lady Shiva twice, once when he was still in training; defeated Deathstroke without problems in his 2nd year; beat up Killer Croc; and Bane did the backbreaker on him....and COULDN'T break his back, unlike in the comics and Nolanverse. Really nothing more to be said.
The first game, Batman: Arkham Asylum, gives us an actually scary version of the Scarecrow. In other media, Scarecrow was just a guy dressed in a crappy Halloween costume who relied on his hallucinating drugs to strike terror in his victims. In the game, he's a Manipulative Bastard and an Evil Genius who can cause psychological horror without using his drugs. His biography describes him as one of Batman's most dangerously psychologically challenging foes. For good reason too. It gets taken to all new levels later when he becomes the Big Bad of Batman: Arkham Knight and becomes the first villain in any version of Batman ever to unmask him to the world.
Whilst Tim Drake in the comics is by no means un-badass, his Batman: Arkham City appearance definitely seems to be aiming for a grittier approach to the character, with a far more chiseled and muscled appearance, a buzz cut, and the idea that he takes part in cage-fighting in his spare time.
While most incarnations of Jason Todd are badasses in their own right, none of them are at the level of the incarnation in Arkham Knight, who leads an army of professional killers as the titular Arkham Knight, specifically trained by him to kill Batman and manages to take over Gotham in mere hours.
In the comics and most adaptations, Hugo Strange is a criminal mastermind or conman whereas in Arkham City he is a Manipulative Bastard who gets the top on all of Batman's rogues except Joker. Likewise in the comics, Hugo Strange was the first villain to learn of Batman's identity but in the original story, Strange Apparitions, it came about because he trapped Batman and unmasked him and in Prey he managed to trick Batman into revealing it, whereas here he's competent enough as a shrink to create an accurate psychological profile of Batman from a distance.
Calendar Man goes from a Harmless gimmick villain to being a vicious serial killer who is genuinely menacing, the Riddler's Super OCD leads him to build many a Death Trap, serving as a Wild Card who creates a network of informants in different factions and as an unofficial Knowledge Broker for Gotham's underworld. Mr. Freeze and Clayface likewise have a larger profile in these games, with Mr. Freeze providing Batman the most intricate Boss Fight of the entire series and Clayface being the Final Boss of Arkham City, providing the largest character model as well as being one of the few villains Batman uses lethal force against.
Taizo Hori, hero of the original Dig Dug, and member of the Mr. Driller cast, pictured on the main page in his appearance in Namco X Capcom. Besides changing his look to one that's more realistic and rugged, the game also altered his background so that he's a former soldier in addition to being a digger. Actually, Namco X Capcom has a lot of this.
Ditto for Hudson's Bomberman and Lode Runner. Although you'll never see Lode Runner's new look without playing the cell phone version of this game. And, after all, new Lode Runner will look like a kid. Yeah...
Sierra, on the other hand, made him look like a more matured adventurer.
In Warhammer 40,000, the Tau Fire Warrior is a basic grunt unit. When adapted to Fire Warrior, the eponymous Tau grunt is able to single-handedly take on the forces of Chaos, and be able to take out several contingents of the Emperor's finest Space Marines. The novel, however, delves into some of the Tau lore and explains it a bit better: Kais is fighting a different battle, only his enemy is the very warlike and self destructive aspect that pushed the Tau to the verge of extinction that they thought they no longer had to worry about. His mentor explains that it is something every Fire Warrior has to face and come to grips with.
In the prequel, Laguna Loire also got this treatment. In his original game, he wasn't particularly special in combat, he fired a couple blasts from his trademark machine gun as his normal attack and for a Limit Break threw a grenade and fired his machine gun double-time. In Dissidia 012? He's the living embodiment of More Dakka, packing rocket launchers, a machine gun, various types of grenade, a sniper rifle, and a giant laser cannon in the shape of the airship Ragnarok. And his Limit Break? Calling all his weapons together to form a Wave Motion Gun.
One of the largest upgrades happens in Final Fantasy VII with spells. Meteor and Holy had been recurring powerful Black and White spells, respectively. In the seventh installment they are boosted far beyond that to plot devices as the Black and White Materia and were capable of wiping out or defending the entire planet. The series-wide reference was lost for most western audiences due to the then lack of previous installments and inconsistent translation.note Holy was renamed to Fade, White, and Pearl in the three that made it over.
Donald goes from a short tempered household name to a Badass Abnormal, Goofy is a Badass Normal who fight just as well as the characters WITH magic. Minnie may also count but we only get so little out of that escort mission in Kingdom Hearts II.
Of course, this is just an expansion of the currently underutilized in America side of Mickey as a great adventurer. Comics have always been a place for his badass side to shine, especially in Italy.
In Wonderland at least, in the second game it's driven home that in the real world, Alice faces the very real dangers of being a mentally unstable teenage girl in Industrial Revolution London.
The Hobbit from 2003 does this to Bilbo. Sure, he doesn't get to fight trolls or dragons but he can fight hordes of goblins, giant spiders, the undead and liches. He can break enemy shields with his sword, and create a shockwave on the floor with his walking stick that sends enemies flying. And he can pole vault with the stick too.
The guy from Minecraft (who's apparently named Steve? (? included)) got this kind of treatment in his cameo appearance in the PC version of Super Meat Boy. Just like in Minecraft Steve? can both lay blocks in the game world as well as dig through anything, making the usually challenging platforming game comically easy. Essentially this ability goes so far beyond game breaking that Steve? is basically bending the game over a table and having his way with it.
Bumblebee in his Transformers: War for Cybertron incarnation is a Hot-Blooded playable character who can easily rack up a triple-digit kill count over the course of the Autobot campaign. He doesn't have the raw power of Optimus Prime but he makes up for it with speed, skill and determination.
Starscream in Transformers: Fall of Cybertron is probably the deadliest incarnation of the Decepticon to ever exist. For starters, he actually fights his enemies. Except for Megatron of course, but he did take on Optimus Prime. Despite his failures as a leader, Starscream is not a force to be reckoned with in this story.
In Persona Q, due to the change in gameplay where everyone has a main Persona and a secondary Persona that adds moves, HP, and SP, the starting Personas for the Persona 3 and Persona 4, which are respectively Orpheus and Izanagi, are now on par with the rest of the casts' own Personas and level up normally. In their home games, they are starter Personas that are intended to be fused after Level 6 or so, due to how the nature of how their home games' fusion system works. Orpheus in particular is weak to two elements, and while he's still initially weak to them, in Q, when he evolves into Messiah, he'll lose is weakness to lightning; Izanagi will similarly lose his wind weakness when he becomes Izanagi-no-Okami.
Some of the gods in the God of War Series are depicted as being much stronger than the Greek Myths presented them as. Ares, the Big Bad of the first game, is presented as a titanic warrior the requires a MacGuffin for Kratos to have a fighting chance against, where in the Greek myths he was a coward that would run away from a fight at the first sign of trouble despite being immortal (though Ares as an Adaptational Badass is also done in every other adaption of him—including Roman mythology), and Persephone in Chains of Olympus, who was simply mentioned as being dragged off by Hades in the Greek myths, is presented as being able to fight Kratos in hand-to-hand combat.
Fist of the North Star: Ken's Rage featured Mamiya as a full playable character. In the series, she was shown to be reasonably affective against small groups of Mooks, but against large forces or serious Martial Artist types, she'd inevitably turn into a Distressed Damsel in need of rescuing. Being a playable character, however, means that she's now fighting on par with Kenshiro himself - tearing through armies of hundreds if not thousands, and singlehandedly disassembling top-tier bosses. It probably helps that she's picked up an Automatic Crossbow somewhere - heck, she can even pull a SECOND one out of Hammer Space for one of her Signature Moves.
Liu Shan in the original Romance of the Three Kingdoms is the definition of Sucksessor, completely inept at fighting and ruling, and in the first sight of danger, he surrenders. Dynasty Warriors turns him into an actually Badass Pacifist by the virtue of being playable. Not exactly top tier, but much more competent, savvy and in a way, virtuous like his dad, although he's a bit scatterbrained (or so he presents himself to public). On the assault on Cheng Du, he fought against Sima Zhao first before retreating, rather than surrendering on sight. Only after their next encounter he surrenders. note And the reason he surrenders wasn't because he's scared as hell, but to preserve the people of Shu from the Hopeless War brought forth by his subordinates who simply doesn't know when to quit. In 8, the implication of Hopeless War and 'subordinates who doesn't know when to quit' is absent, but Liu Shan still fought Sima Zhao as the latter enters the throne room to the end before surrendering.
Arthur from Ghosts N Goblins is a little guy in a suit of armor. When he appeared in Cannon Spike, he notably was changed into a giant, muscular weapon of destruction.
Jack Driscoll in the 2005 version of King Kong was a pretty meek guy whose every attempt at being heroic always inevitably failed. In Peter Jackson's King Kong: The Official Game of the Movie, however, he's the human Player Character. Despite having no military training, he wields a variety of firearms, can throw spears like a pro, and kills all sorts of dinosaurs and monsters before getting off the island.
When Freddy Krueger first showed up in Mortal Kombat 9 he seemed like more of an Adaptational Wimp, having lost most of his supernatural powers and being forced to rely almost entirely on his Wolverine Claws to fight. Then you remember that he only has his powers in the dream world while in the physical world he's pretty much just a foul-tempered burn victim with knives on his hands. In the movies, getting dragged into the physical world is basically a death sentence for Freddy, as the first movie in the franchise showed us he can't even outfight an untrained teenage girl in the real world. So watching him hold his own against people like Liu-Kang and Shang Tsung without his nightmare powers is actually pretty incredible.
Bass.EXE from the Mega Man Battle Network series. when compared to Bass from the classic series, he went from a somewhat challenging rival of Mega Man to theBonus Boss of the franchise, and with good reason. He is also considerably more unhinged than in the Original series.
Injustice: Gods Among Us Characters like Batman are shown being able to survive being punched into orbit thanks to competitive balance. In-universe, it's the use of Kryptonian nanomachines that handwaves Badass Normal characters being able to fight toe-to-toe with Superman.
Dynasty Warriors: Gundam turns a few notable Gundam characters into this, most notably Elle Vianno, who was pretty inept with the Gundam Mk-II, and Lacus Clyne, whose only moment of piloting a Mobile Suit was guiding the Infinite Justice down to Earth.
Super Dragon Ball Z had a small cast of characters compared to the likes of Dragon Ball Z: Budokai or Dragon Ball Z: Budokai Tenkaichi, but one character playable only in Super in particular stands out: Goku's wife, Chichi. In the original manga and anime, she hardly does any fighting after becoming a mother, and yet here she is, Power Pole and Bansho Fan in hand, throwing down with the likes of Frieza, Cell, and Majin Buu.
Captain Ginyu becomes one in Dragonball Xenoverse - in the animé/manga, he couldn't use the techniques of those he changed bodies with. Here, however, he's able to use Goku's Kamehameha and even go Super Saiyan with no difficulty.
Also from the same game is Krillin. In the original series, his attempt to cut Vegeta's tail to revert him from his great ape form to his original form failed, and it was Yajirobe who did it. In Xenoverse, Krillin succeeded in cutting off Vegeta's tail, and it's treated as if he did the same thing in the original timeline as well.
Enforced by plot in Alien: Isolation, thanks to the addition of non-xenomorph enemies and actual weapons combined with the retention of the originally planned "sneak and hide focused" Survival Horror gameplay. In the movie continuities, xenomorphs are dangerous, but of a "Glass Cannon with acidic blood" flavor, being difficult to kill only when they can't be allowed to bleed or the humans have no weapons. In the game, the lone xenomorph is, by demands of the plot, an Implacable Man, which can't be more than staggered by any weapons the player has. This can be handwavedto an extent (the flamethrower is a jury-rigged piece of junk, the pistol and shotgun are deliberately low-velocity to avoid hull-breaches, the technology in general is less advanced than that in the second film), but when pipe bombs detonated right at the alien's feet merely scare it off, and it's immune to the bolt gun, which can oneshot kill Working Joes. This has led to backlash.
All the classes from Ragnarok Online that show up in Ragnarok Battle Offline got themselves some massive power boosts, in order to be able to deal with the many bosses that are tossed in their direction, who are also taken from Ragnarok Online and didn't exactly lose power. Curiously, some particular attacks got buffed hard enough to qualify for this, like Magnum Break going from a mediocre Splash Damage hit to a fiery whirl of sharpened death, and Lightning Storm going from a crappy AOE attack to an electric cataclysm that can fry screens worth of monsters.
Hyrule Warriors does this quite extensively, as The Legend of Zelda does depend on the player via Link being the only chosen hero. The player characters vary in how they approach this. Some, such as Shiek, Darunia and Midna were implied badasses in their own games, but we never got to see them act that way. Zelda and Impa have been implied to be badasses in some of their games, but make the jump to full-fledged badasses here. And then there are those who became badasses totally under their own merit — the most prominent example of this is Agitha, who was just a slightly loopy sidequest-giver in The Legend of Zelda: Twilight Princess.
Bandit Keith is at his best in Yu-Gi-Oh! Reshef of Destruction. In the Yu-Gi-Oh! manga, he was a washed-up has-been who lost to a rookie in spite of cheating, and the anime version of him was cooler, but not by a large margin. In this game he leads the Neo Ghouls in taking over Domino, kidnapping Ishizu, and seizing the Winged Dragon of Ra, which he then duels the player with. Even after he loses the duel, he then gets you to hand over Ra anyway, and is only defeated when the card fries him with lightning. And even then, he's promptly possessed by Reshef, gets back up, and breaks the Millennium Puzzle, which lets Para and Dox steal the pieces and capture Yami Yugi.
In Yu-Gi-Oh! 5D's, Devack was a villain whose story arc was cut short, and he didn't have much presence. In Yu Gi Oh BAM, he's a major villain and brainwashes you, your friends, and Kaiba thanks to his neuro-needles.
Smug Snake Dolores Umbridge gets this trope of all people in Lego Harry Potter: Years 5-7. In the original books, she is portrayed as mean, but very incompetent when it comes to actual magical knowledge and ability and is never shown participating in real combat. However, when a herd of angry centaurs fire arrows at her in the game, she employs some impressive martial arts moves, such as casually avoiding an arrow, followed a backflip and even kicking one arrow away. She is also a boss fight in the final year, in contrast to the books, where she is knocked out by a single spell.
Call of Cthulhu: Dark Corners of the Earth does this to the main character. In the original story The Shadow Over Innsmouth the main character visits Innsmouth on a whim and is chased out of town before passing out from terror upon seeing a Deep One. His involvement with Innsmouth ends there as the authorities take over. In the game, that's only the end of the first half of the game, with the second half seeing him return to Innsmouth with Hoover, the FBI, and the U.S. Marine Corps and personally destroying the Marsh family and the Deep Ones.
Due to its crossover nature, many a party member in Rakenzarn Tales ends up being much tougher. For example, Dirk the Daring was already badass, but here he can take more than one hit before dying. Ed, Edd n Eddy are surprisingly viable combat choices. The normally goofy Derpy Hooves can fight on the front lines as well as anyone else. And Kyuu is poised to become the most powerful party member in the game with proper training.