Switched from "good to evil" or "evil to good."
Michael Corleone - Godfather (1972)
WWII hero turned head of murderous crime family
Captain America: The Winter Soldier (2014)
Military hero suffers amnesia and brainwashed to become the evil Winter Soldier. Then back to being a good guy.
Jaws - Moonraker (1979)
Murderous mercenary suddenly becomes good and helps defeat the villain.
Link - Red Sun (1972)
After leading bandits to rob a train of money and killing many soldiers, he eventually fulfills a samurai's dying wish.