In the movie 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 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.
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 Nazgűl 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.
Iron Man 3 does this to Aldrich Killian. In the comic book storyline Extremis, Killian commits suicide at the start of the comic after being spurned by Tony. In the movie, Killian initially looks like he will follow his comic counterpart, but does not go through with it and becomes the main villain of the movie. He is revealed to be the real Mandarin, orchestrating terrorist attacks using the Extremis formula and posing a very large threat throughout the movie.
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 who roughs up a woman, and later gets unceremoniously killed 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.
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.
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.
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 a European king, 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 outmaneuvers 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 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 badassBounty Hunter the fandom wanted him to be.
In the Superman comics, General Zod was one of Krytpon'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. In Man of Steel, Zod is even genetically bred and trained for war; and proves to be more than a match for Superman before getting the full range of yellow sun powers.
Teenage Mutant Ninja Turtles (2014). The eponymous Ninja Turtles were previously meant to be mostly human-level in strength despite being mutants, as their main skill was their ninja abilities. The movie gives them some very impressive humvee-crushing super strength and in general are extremely acrobatic compared to previous incarnations.
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.
V for Vendetta features a tricky one for Gordon Dietrich. The movie turns him into a chubby, middle-aged comedian (played by Stephen Fry, no less) when he was a younger, more physically imposing career criminal in the book. Then again, the film also has him defying the Party'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 character did in the book.
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.
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 in X-Men, 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.
In the comics, 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 the third film, he attached to his glove, allowing maximum firepower with minimum inconvenience.
Much like the Peggy Carter example from Captain America, Mariko Yashida is a much more capable and physical badass in The Wolverine.
In the comics, the Sentinels are just Humongous Mecha, and mutants with strong powers note 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 '70s of X-Men: Days of Future Past 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.