The African Queen: the titular ship actually succeeds in destroying the German warship "Louisa" (actually Königin Luise) even after capsizing herself in a storm, as the "Louisa" happens to run into the overturned African Queen, striking the detonators of Charlie Alnutt's home-made "torpedos". In C. S. Forester's novel the Queen anticlimactically sinks in a storm and the "Louisa" is finally sunk by two modern British gunboats transported piece by piece overland and then assembled on the west coast of the East African lake. (In the film the captain of the "Louisa" also receives a villain upgrade, condemning Charlie and Rosie to be hanged. In the novel he decides it would be uncivilised to have the two executed as spies so he hands them over to the British under a flag of truce).
Tim Burton's film adaptation of Alice in Wonderland (2010) gives the Mad Hatter this treatment; he goes from a silly joke character (as most of the cast in the original work) to a silly joke character who charges into battle with a Scottish claymore. Arguably all of the characters in the movie, as well, to some degree.
Following the examples set by Batman: Earth One and Beware the Batman, Alfred is said to be more hand-on in helping Batman. In fact, much like in Earth One and Beware, this Alfred was the Wayne family's bodyguard, not their butler.
Thomas and Martha Wayne are depicted as going out fighting on the night they got killed.
While Doomsday was never weak, he was still beaten by Superman alone. Here, the combined might of Superman, Batman, and Wonder Woman doesn't faze him and he only fell when Superman sacrificed himself to stop him with a kryptonite spear. In addition, Doomsday is roughly fifteen feet tall instead of eight, has the ability to absorb energy, and has heat vision and a Nuclear Pulse-like attack.
In Batman: The Dark Knight Returns, one of BvS's major influences, a not-fully recovered Batman fought a weakened Superman with the help of Green Arrow and the fight ended in a draw thanks to Bruce faking his own death. In the movie, both Batman and Superman are at full health and Batman fights Superman solo—and actually beats Superman, almost killing him. Clark pleading him with to save Martha Kent as she was taken hostage by Luthor, Bruce flashing back to the night his parents died, and Lois explaining who Martha Kent is are what saved Clark and snapped Bruce out of his murderous rage.
The live-action movies of Death Note turn L, who was already a genius and capoeira trained badass in the original source material, and have him take down Light, a reversal from the original material where L was killed by Light.
Oddly enough, from Dragonball Evolution, the Kamehameha Wave. In the source material it's a powerful attack, the strength of which is limited only by how much energy its user can put into it, but that's about it. In the movie it becomes a Swiss-Army Superpower. We see it used to light and extinguish fires, and even to heal a person from near death!
Harry Potter films took this both ways with Buckbeak. On one hand, they gave Buckbeak his own Crowning Moment of Awesome by showing him protect Harry and Hermione from the werewolf, which wasn't in the book. On the other hand, the sixth and seventh books described him flying around attacking Death Eaters, which wasn't in the movies. A borderline example, if you will.
Bilbo Baggins is a lot more quick-witted, competent and takes the initiative in the movie, and on several occasions—most notably the encounter with the Trolls—manages to accomplish more in moments where he was saved by someone else in the book. In the book, he doesn't really start pulling his weight until he saves the Company from the spiders, while the movie gives him a Big Damn Heroes moment saving Thorin from Azog immediately following the Goblin encounter.
The dwarf company is more badass than they were in the book. All armed to the teeth, they are raking in high kill-counts in many scenes where they simply slipped away unnoticed or with minimal trouble, like Goblin Town and the Barrel Ride.
Radagast the Brown from the books was something of a coward and abandoned his mission because he couldn't gather the courage to face the Nazgûl head on. In the first film he faces off the Witch-King of Angmar without a hint of fear or hesitation, only escaping when he comes face to face with Sauron himself.
The Hunger Games: Peeta sees a lot more action in the films than in the books; being able to hold his own against Cato on top of the Cornucopia in the first, and overpowering and drowning another tribute in the second.
On the other hand, the movies fail to show him fighting at the Cornucopia, fighting Cato after the tracker jacker attack and killing Brutus.
In the book Live and Let Die, Tee Hee's a perfectly ordinary mook whose only quirk is giggling while torturing people and who dies very early on. The film adaptation of the story ups him to second-in-command to Mr. Big.
Jaws in The Spy Who Loved Me. He is loosely based on the villain Sol "Horror" Horowitz from Ian Fleming's novel of the same name, who is a thug with a metal-capped teeth whose villainy is limited to terrorizing a helpless woman. He later gets unceremoniously killed by Bond as he tries to make a getaway on a car (and is outlived by his partner, who became Sandor in the same film). Jaws, however, is a man who just won't die, and is one of the most remembered aspects of the film, and its subsequent sequel.
Skyfall does this to Miss Eve Moneypenny and to lesser extent, Ralph Fiennes' Gareth Mallory, the new M after the death of Judy Dench's M.
Depending on the movie, Bond himself may count. Fleming's books (at least, the early ones) tend to be less splashy affairs than the movies, and Bond often gets his ass handed to him by the villain and/or his henchmen. Meanwhile, some of the movies portray him as a Made of IronOne-Man Army who can mow down dozens of mooks without stopping for a breath.
Supporting villain Tal Hajus was a lazy Villainous Glutton who rarely moved from his throne (and got curbstomped in less than a paragraph when he did move). In the film he's in much better shape, much more active, and apparently younger, though he still gets curbstomped. Being a Big Bad Wannabe in an action/adventure story apparently doesn't let you catch a break.
Mowgli in this one is inventive, clever, and brave, unlike his '67 counterpart.
Baloo too. In the original cartoon, Baloo grabs Shere Khan by the tail and is dragged around a lot. In this movie, he helps Bagheera in fighting the monkeys and fights Shere Khan with brute force, teeth, and claws. He actually almost wins the fight until Shere Khan deals a blow to the neck. It doesn't kill Baloo, but it's enough to finally get him out of the fight.
Iron Man: The main hero himself, or at least, his early armours, which are far more powerful than the earlier armours Tony employed in the comics. His most traditional armour tends to only include repulsars and the Uni-beam as weapons, but the film also adds in a lot of hidden missiles and weapons, and draws more from the later armour models than the original versions.
Combined with Adaptation Distillation and Composite Character; in the comic, Whiplash was just a guy with a bullet proof-though ridiculous looking costume and two lashes, who while he could take on Iron Man's early armours, he was easily out-matched when Tony got some upgrades. Iron Man 2 mixed him with another villain called Crimson Dynamo and revised him as a Genius Bruiser and Magnificent Bastard who could actually hurt Iron Man's more advanced armour.
Iron Man 3 does this to Aldrich Killian. In the comic book storyline Extremis, Killian commits suicide at the start of the comic, out of guilt over selling Extremis to a Right-Wing Militia Fanatic. In the movie, Killian becomes the main villain of the movie, as he is revealed to be the real Mandarin, orchestrating terrorist attacks using the Extremis formula and posing a very large threat throughout the movie. He also takes Extremis himself, becoming physically powerful enough to demolish Tony's armours with his bare hands.
Subverted in Captain America: The Winter Soldier with Georges Batroc, known in the Marvel Comics as Batroc the Leaper; traditionally a Badass NormalNoble Demon who regularly goes toe to toe with Cap and always puts up a pretty impressive fight, but is often assumed to be a joke because he's French and has a hideous costume design. In the film, he's just as badass as he is in the comics, but with his more silly characteristics removed, and played by Mixed Martial Arts champion Georges St-Pierre.
The Vision is not nearly as important or powerful in the comics as he is in Avengers: Age of Ultron. In the comics he has a pretty standard powerset - flight, higher than average toughness and strength, density manipulation powers, and a beam weapon in his solar-powered gem. His origin was also basically an android given life by copying the brain of another existing superhero. He is also the Avenger most often destroyed because he can be easily rebuilt. After being destroyed again, he was literally left in the Avenger's warehouse for years and was not present during major story arcs like Civil War. He has only been written back into the comics in the last 3 years. However in the movie, his origin and power level are far more impressive, where it takes Thor's lightning to give him life, has vibranium incorporated right into his cells which makes him nigh indestructible, and being powered by one of the Infinity Gems raises his power potential far above his original nameless solar gem. And he is able to wield Mjölnir and thus judged 'worthy', a privilege that not many Marvel in either the Marvel Cinematic Universe or the comics can claim.
Night of the Living Dead (1990) does this to Barbra. In the original film, she became a near catatonic load from all the horror surrounding her. In the remake, she takes an active role in defending the house from the zombies, to the point of being the sole survivor in the end.
In The Wonderful Wizard of Oz, Glinda is a relatively tame character that does help the heroes, though through indirect means, which translated into The Wizard of Oz. In Oz: The Great and Powerful'', Glinda is a much more active character seeking to avenge the death of her father, the previous wizard who uses her magic to battle the Wicked Witch of the West and play a large part in getting the people of Oz to revolt against the Wicked Witch.
The Wicked Witch of the West herself. In the book and the 1939 film, she does have spells that can help her accomplish her goals, (including poppies and an enchanted hourglass that ends a person's life when the sand runs through it); but both are foiled (by Glinda's snow and The Scarecrow, Tin Man, and Cowardly Lion rescuing Dorothy) and she ultimately meets her end by being splashed with water. Now, she has fire-based magic and actively tries to harm the people of Oz in part for being manipulated into becoming the Wicked Witch of the West.
Rurouni Kenshin: the eponymous hero is more competent in unarmed combat. In the source material, Kenshin is more or less useless without a sword.
Daphne in Scooby-Doo was transformed this way. She even beats someone up in the live action film.
Holmes and Watson's portrayal, although not nearly to the degree that some viewers accused it. Watson was a veteran Army doctor in the books, while Holmes was a martial artist and bare knuckle boxer with surprising strength. The movie turns them both into outright action heroes who take on multiple opponents at once in hand-to-hand combat and defeat all manner of armed attackers.
Irene Adler as well. In the book, she was a singer/adventuress who had a fling with the King of Bohemia, and Holmes was hired by the king to recover some letters he wrote to her, so they don't end up embarrassing him later. Her main distinction is that she outmanoeuvres Holmes and moves the letters beyond his reach, leaving a note to Holmes in their former hiding place. For this, she earns Holmes' respect, and he always afterwards refers to her as the woman. In the movies, she is a brilliant career criminal who is more than capable of defending herself. At one point she is mugged, and she turns the tables, mugging her muggers.
Star Trek Into Darkness gives this treatment to Khan. Not that Khan wasn't always a badass, being genetically enhanced, but his strength only made him one of Kirk's most difficult adversaries, and capable of being defeated with a blunt weapon. This version of Khan is much more physically powerful, a One-Man Army able to wield what looks like a converted starship weapon single handed. He could take just about any amount of physical punishment and keep fighting, as well as take multiple stun shots from a phaser (and No Selling the Vulcan Neck Grip) before going down.
Star Wars: Boba Fett in the films misses every shot and gets knocked into a Sarlaac pit by a blind man. The dozens of books, comics, and video games that have used him since have ignored this in the interests of making him the badass Bounty Hunter the fandom wanted him to be. The Clone Wars shows that he was like this even as a child.
In the Superman comics, General Zod was one of Krypton's top military advisors, but often relied more on his planning skills than doing actual fighting. The character's film portrayals have helped make him a much bigger threat. Superman II portrayed Zod as a charismatic leader that took full advantage of the fact that the gained powers from Earth's yellow sun; as displayed in the film's fight scenes. It proved to be so successful that it was integrated into the comics and became a key factor in every subsequent adaptation that featured Zod, not to mention several other Kryptonian villains. There's also the aforementioned Man of Steel.
Bumblebee's main role in the original cartoon was evacuating the humans to safety while the bigger, tougher Autobots went into action, and that was about it. In the film series, he has a Decepticon kill count second only to Optimus Prime himself, and he's the go-to guy for being a Big Damn Hero, and is quite badass in Transformers Prime as well.
From the third film, Sentinel Prime, who mostly appeared in comic series to serve as Optimus Prime's predecessor who gets killed by Megatron, and in as a Jerkass in Transformers Animated who got beat up every appearance he made. Here, he's Optimus Prime's mentor and never made out to be helpless and after being revealed as the film's Big Bad, actually defeats Optimus in both their fights.
Starscream was considerably more badass than almost all of his previous incarnations in the first live-action film, where he holds his own against Ironhide and Ratchet, easily destroys military aircraft, and is one of the few Decepticons to survive the movie. However, this was inverted in the sequels, to the point where he became one of the most pathetic of the Decepticons, although given that he was beaten up both by Optimus and Megatron, this is somewhat understandable.
Hound was originally a pacifist who used his wits and holographic projector against his enemies. In Transformers: Age of Extinction, he's a rude and crude fatass-badass who kills enemies left and right, all whilst cracking jokes about his stature.
V for Vendetta features a tricky one for Gordon Dietrich. On the one hand, the film makes him a chubby, middle-aged comedian (played by Stephen Fry, no less) while he was a younger, more physically imposing career criminal in the book. On the other, in the film he defies Norsefire Government's laws by hiding banned books and films in his house, and openly mocking Chancellor Sutler on his show (which he is eventually executed for), which is far more badass than anything the Novel!Gordon did.
Gul'dan in WarCraft gets this treatment. While, like his video game counterpart, he mostly acts from distance and casts spells, when challenged to mak'gora, he holds his own extremely well and wrecks his enemy as much as the other guy does.
Pretty much every non-powered hero in Watchmen becomes a lot tougher and a lot stronger in the movie version of Watchmen. The film also removes a lot of the deconstruction of super-heroes that intentionally made them seem a bit ridiculous.
Lawrence Talbot in The Wolfman (2010). His Wolfman is far more formidable than in The Wolfman 1941, killing about 10 times the number of people the original Wolfman did. Even in human form, he's not bad with a rifle.
The comic book version of Pyro was a Laughing Mad pyrokinetic who was hamstrung by his inability to create flames, relying on an unwieldy pair of flame throwers with very prominent fuel lines. Naturally, he was often very easily hamstrung. In the films, he's perfectly rational, albeit a bit temperamental, and he now only relies on a lighter, which in X-Men: The Last Stand, he attached to his glove, allowing maximum firepower with minimum inconvenience.
Quicksilver is one of the fastest characters in the Marvel comics universe, but he has limitations on just how fast, and is generally well under the speed of sound. In X-Men: Days of Future Past, Hank mistakes him for a teleporter, and fans have noted that Peter's Super Speed and power set (he's capable of redirecting bullets with ease and shattering glass by vibrating his hands) are closer to The Flash, who explicitly has a speed advantage over Quicksilver in inter-company crossover stories. It's taken Up to Eleven in X-Men: Apocalypse because he rescues all of Xavier's students from an explosion in only a fraction of a second. Maximoff is one of the most powerful mutants in the whole X-Men film franchise.
X-Men: In the comics, Toad was originally conceived as a deformed, sniveling hunchback who served as The Igor to Magneto. His super power was he could hop... really high because of having very low-grade super-strength, concentrated in his legs. However, stuntman Ray Park played him as a wisecracking martial artist with wall-crawling abilities and a tongue that he could use as a whip, thus making him more capable of holding his own in a fight with other heroes. Also, he could spit slime projectiles. However, considering that Ray Park once played as that red-skinned badass Sith, his badassery has to be expected.
The Wolverine: Mariko Yashida is a much more capable and physical badass than her comic book counterpart.
X-Men: Days of Future Past: In the comics, the Sentinels are just Humongous Mecha, and mutants with strong powersnote the X-Men in the comics are much stronger than in the movies with Storm, Magneto, Iceman, and Xavier being planetary threats; and it doesn't help that they're made of metal usually take them down by the dozen. They are portrayed as such in the 1973 portion of the film as well. The future Sentinels, however, with their ability to duplicate mutant powers to counter their opponents, are so overwhelmingly powerful that any fight with them is considered outright hopeless.
X-Men: Apocalypse: In the comics, Angel is sometimes mocked for lacking any sort of offensive capabilities before becoming Archangel. In Apocalypse, he has sharp talons on his wings, making him a formidable physical threat even before he gains his metal wings and Feather Flechettes.