Admit it, you heard the soundtrack begin the moment you saw this image.
In Return of the Jedi, Darth Vader diessaving his son from Emperor Palpatine. One of the most iconic moments of the saga, also this page's image. The especially cool part of this is that it involves an actual wrestling move. Redemption Equals Death doesn't apply quite so much here, as thanks to his redemption, he's reborn as a Jedi ghost.
Alice in Seventh Son ultimately betrays the witches to help her love interest, witch-hunter Tom.
In Iron Man Tony sums up his new change in direction to Obadiah when he chews him out for shutting down the weapons enterprise of Stark Industries;
Tony: We're not doing good enough, we can do better, we can do something else.
Avengers: Age of Ultron: After Wanda Maximoff reads the subconscious thoughts of Ultron through the Vision's body while Ultron is Brain Uploading himself into it, she finds out his plan to annihilate mankind, and quickly changes sides with her brother Pietro.
Guardians of the Galaxy Vol. 2: Nebula struggles with joining the Guardians and ends the film on their side, but leaves to continue her crusade against Thanos. In Avengers: Infinity War she is fully on the heroes' side, even going as far as to find the Guardians and tell them what happened.
Captain Louis Renault, in Casablanca. It's arguable how much of this is heel-face turn and how much of it is a hidden Face awaiting the moment when his turn will do the greatest good. However it qualifies under the criteria that the audience isn't sure what side he's on until he makes his stand.
Tiffany Case in Diamonds Are Forever was a diamond smuggler and (although unknown to her) part of Blofeld's diamond-smuggling ring, but later helps Bond in taking him down.
Jaws in Moonraker, after spending most of the film as one one of the main henchmen (and being the main henchman of the previous one), after being forced to choose between his employer and his girlfriend, he chose the latter.
Octopussy and her group in Octopussy were part of Kamal Khan's Fabergé Egg-smuggling plot (and in fact, Octopussy seemed to be his boss), but when he teams up with a Renegade Russian who plans to engineer a nuclear explosion and realises that she, her crew and thousands of innocents would have been caught up in the explosion, they turns against him.
May Day in A View to a Kill was Max Zorin's main henchwoman, but she eventually foils his plans to flood Silicon Valley after he kills her own two henchwomen as part of his plan and reveals that he always thought of another guy, Scarpine, as his true right-hand man.
Valentin Zukovsky in GoldenEye was a Russian gangster in the past, but by the time of the film helps Bond in looking for the villain (though he claims that it's out of him hating the villain as much as Bond does).
Godzilla himself goes from city-destroying villain to world-saving hero during the 1960s-1970s. His Heel Face Turn occurred when Mothra convinced him and Rodan to fight King Ghidorah in the 1964 film Ghidorah, the Three-Headed Monster.
An example of a Heel Face Turn already accomplished by the time of the story is that of the convict in The Dark Knight who threw the detonator out the porthole after rebuking the guards for not having already done it.
Subverted in Terminator 2: Judgment Day, the reprogrammed T-800 Model 101 isn't the same terminator from the first film. Double Subverted in that it was probably also programmed to kill humans before John Connor captured it, though.
In the Hairspray musical, both Velma and Amber Von Tussle are redeemed through the power of THE BEAT, but in the film adaptation, only Amber seems to have one; accepting her loss and walking away from her mother to talk and dance with one of the black dancers.
In The Muppet Movie, Doc Hopper's old friend Max dressed like a police officer in order chase the Muppets bus and warned Kermit that Doc Hopper has hired a professional frog killer. And the man is really deadly.
The Operative undergoes one of these at the end of Serenity when he discovers the truth behind the secret of Miranda, and just what the utopia he has been fighting for all this time would really look like.
At the end of The Terminal, Dixon, the customs commissioner who has been trying to get Viktor to leave the airport, even illegally, throughout the film so he won't have to deal with him, has told Viktor to go back to his home country now that its civil war has ended and he can return. He threatens retaliation against all of Viktor's friends should he attempt to go to Manhattan and complete his quest. But, having been diverted from seeing Viktor actually leave, he tells the customs officers to get ready for the next incoming flight instead of going after him.
In Pixels, both Q*Bert and Lady Lisa join the heroes - the first because he doesn't want to see Earth destroyed, and the second thanks to the Power of Love.
Cameron Diaz's character from Bad Teacher starts out a Golddigger and an Apathetic Teacher, but after her talk with Garett about his crush she realizes she is no different from anyone else and becomes the school's guidance councelor.
Sorsha in Willow, after she shacks up with Madmartegan.
A slow, detailed one of these is roughly the entire plot of the German film The Lives of Others (Das Leben der Anderen).
Zangief in the Street Fighter movie is mainly the Plucky Comic Relief of everyone in Shadaloo, but after Dee Jay informs him that Bison is "the bad guy", he helps the heroes escape. Zangief and Dee Jay weren't evil in the games.
Sgt. Hugo Stiglitz, a former Nazi enlisted man who turned on his superiors and murdered 16 Gestapo officers before being jailed, condemned to death, and ultimately rescued and recruited by the Basterds. Granted it's implied he's simply a serial killer, but he's at worst a Soft-Spoken Sadist and all his murder victims are the decidedly more evil Nazis, which is heroic enough for this list.
the main villain Hans Landa discovers the Basterds' plot to kill Hitler and decides to help them, striking a deal with the Allies and generously demanding medals for the Basterds' bravery. This is all subverted by the fact that Landa is acting purely on whim and self-interest, and is still a total slimeball. Ultimately Aldo is well aware of this, and treats him accordingly.
In Pineapple Express, Red first tries to help the villains kill the heroes, but ultimately comes to their rescue and becomes best friends with them.
In The Cook, the Thief, His Wife and Her Lover, Cory the pimp starts as a member of Spica's gang, but gets ejected after he resists Spica's brutal treatment of his girls. He ultimately joins the final confrontation with Spica.
In Get Shorty, Bear starts as a thug for Bo Catlett, but eventually switches to Chili's side.
In Ocean's Eleven, Benedict is the main villain, but by Ocean's 13, he's convinced to support Ocean's gang, though he's still a ruthless bastard.
In Shaolin Soccer, local thugs beat on the monks several times before getting bested in a soccer game and joining their team.
In the documentary An Arctic Tale, the male polar bear is the main villain for most of the film, but near the end he shows compassion for Nanu, the polar bear protagonist, and shares his kill with her. Nanu later finds a mate, but we do not know if it is the same bear.
In Finding Neverland, though Emma is not an evil person, she is the only main character who is consistently antagonistic towards James Barrie. Her attitude changes completely as a result of seeing Peter Pan and Sylvia dying.
Derek and Danny in American History X after they become disillusioned with the Neo-Nazi movement.
The Cobra Kai students at the end of The Karate Kid. Made apparent at the start of the second film where Johnny accepts his loss and he and his friends leave the dojo. Their sensei, on the other hand, remains evil throughout the series.
In the 1982 film version of Annie, Miss Hannigan does a major one near the end. She had always been mean to Annie, a lush, and a less than ideal ward to the orphans. But when she realizes that Rooster chases after Annie hoping to kill her after she tears up the check, she tries to prevent him from doing so.
Number 2 attempts one in Austin Powers: International Man of Mystery before he's eliminated by Dr. Evil. Mini-Me successfully performs one in Austin Powers in Goldmember once Dr. Evil replaces him with Scott, and Dr. Evil himself makes the turn upon learning that he is Austin's long-lost brother Doug. Also Fat Bastard has a change of heart.
The good guys in Escape to Athena easily convince Major Hecht to join them. To establish it before the turn, he is shown to be a Punch-Clock Villain who is displeased to work with the SS.
In G.I. Joe: RetaliationStorm Shadow performs one after he finds out that Zartan was the one who framed him for the murder of his and Snake Eyes' master.
In Byzantium Darvell decides to turn on the Brethren and save Clara's life rather than blindly follow their rules any longer. In the end he asks to journey with her in the hopes she can forgive him for standing by all those years ago.
Magneto seems to have made the turn between X-Men: The Last Stand and his cameo appearance at the end of The Wolverine, because in this movie, Future!Magneto is firmly on Professor X's side throughout and ultimately makes a Heroic Sacrifice against the Sentinels during the climax.
Mystique eventually decides to give up her vendetta against Trask to prevent future bloodshed against Mutants. She also saves Nixon and his cabinet from Magneto.
X-Men: Apocalypse, in the new timeline, Magneto turns against Apocalypse when he realizes that the people he's currently targeting (Mystique and Professor X) are the only loved ones he has left. Storm also makes one when Apocalypse begins attacking Mystique, her idol.
In Annie (2014), Hannigan, after Guy betrays her by hiring the fake parents himself and cutting her out of the deal. She ends up feeling really guilty over her part of the plan to have Annie's "real parents" come take her away, and enlists the girls to get her to Stacks so she can confess.
In Marmoulak, Faezeh's criminal, abusive ex-husband becomes a humble and reformed character after receiving a beating from Reza.
In The Suicide Theory, Steve ultimately turns his back on his hitman lifestyle after bonding with Percival and saving a cop from being shot by a random thug.
Temir and Leo turn against their family at the end of When Darkness Falls after their sister Nina is murdered, to save their other sister Leyla.
The plot of Mad Max: Fury Road kicks off with Immortan Joe's lieutenant Furiosa betraying him to free his "breeders" from slavery. Nux also eventually makes a MookFace Turn when Capable convinces him that it's not yet his time to die.
Captain Gerd Wiesler from The Lives of Others is the brutal, hyper-efficient, seemingly emotionless Villain Protagonist/renowned Stasi master interrogator who is is ordered by his corrupt, morally bankrupt superiors to spy on a playwright just because the East German Minister of Culture lusts after his girlfriend. A dedicated socialist, Gerd begins to empathize with the people he is spying on, becomes disgusted when he learns of the petty reasoning behind the operation, and becomes severely disillusioned with not only his own job and the East German government in general, but also his own life, which is completely devoid of any real connections to other people. He begins lying to his bosses to cover up his targets' actions while also helping them to mend their relationship issues and, by the end of it, he willingly destroys his own career just to save a man he's never actually met's life. After the fall of the Iron Curtain the the reunification of Germany, he lives a seemingly happier life as a postman, and the playwright ultimately anonymously dedicates his latest work to him in gratitude.
In Beauty and the Beast (2017), LeFou gradually starts to find Gaston's behavior questionable and quietly redeems himself, even saving Mrs. Potts during the final battle, and unlike his animated counterpart is seen among the guests at the royal castle at the end of the film.
Warren Peace from the Sky High is a generic bully with pyrokinetic powers who has one evil parent and one good parent. He has it out for Will after his father (The Commander) puts his evil father (Baron Battle) in prison. They duke it out in the cafeteria and Will only comes out on top once his super strength finally manifests itself. They become friends by the end of the movie after defeating Royal Pain and the rest of the villains.
Reform School Girls: Charlie is a major antagonist for most of the film, but when Edna hangs her and her girls out to dry following Lisa's death, Charlie joins Jenny's rebellion against Edna and is ultimately the one who takes her down.
Boarding School: Mrs. Ramsay comes back to the school to pick up her son, not wanting the killer to kill him as she hired him to. Unfortunately, he's already killed the boy and kills her to keep her quiet.
The Terror of Tiny Town: After being under Haines' thumb for all of the film, the sheriff eventually stands up to him and clears Buck of murder.
Warriors of Virtue: General Grillo turns good after Komodo is defeated along with (it's implied) all the rest of his followers, ordering that they release the imprisoned villagers.
Shoot-Out at Medicine Bend: It turns out that hanging innocent men is a step to far for Sheriff Massey. After the Kangaroo Court sentences Maitland and Clegg to hang, it only takes little pushing from Nell to get him to do the right thing and release. He then joins the crusade to bring down Eb Clark. Briefly.
Robot World: One of the Robot Dogs joins the astronaut and accompanies him on his journey across the planet.
In Hellboy (2019), Nimue's first defeat way back when wouldn't have been possible if not for the betrayal of at least one member of her own witch coven. It's implied that this witch had a hand in forging Excalibur, the only weapon capable of actually wounding Nimue.