Master Xehanort

Master Xehanort is the main antagonist of the "Dark Seeker" Saga, the first phase of the Kingdom Hearts video game series. He is responsible for manipulating many events in the game series in his question to unlock Kingdom Hearts by forging the Keyblade. Due to his actions, he can be considered the main antagonist of the Kingdom Hearts franchise.

In Birth by Sleep and Dream Drop Distance, he was voiced by the late Leonard Nimoy in the English dubbed version, who also played Sentinel Prime in the Transformers series, and the late Chikao Ōtsuka in the Japanese dubbed version. In Kingdom Hearts III, he was voiced in the English version by the late Rutger Hauer (who also played Wulfgar in Nighthawks, Roy Batty in Blade Runner, Lothos in Buffy the Vampire, John Ryder in The Hitcher, Huntsman in The 10th Kingdom and Patrick Henry Roark in Sin City) in the base game and by Christopher Lloyd (who also played Kruge in Star Trek III: The Search for Spock and Judge Doom in Who Framed Roger Rabbit) in the ReMind DLC and Kingdom Hearts Melody of Memory. In the Japanese version by Akio Ōtsuka, who is Chikao Ōtsuka's son and also notably does the role of Ansem, Seeker of Darkness and Terra-Xehanort, as well as the voice of Marshall D. Teach in the Japanese version of One Piece.

How He Redeemed Himself?

 * During Kingdom Hearts 3, after being defeated by Sora during his boss battle, he told his true plans which ultimately reveals himself as a Well-Intention Extremist. When his former friend returns from the dead, he accepted his defeat and showed respects towards Sora and decided to move to the Afterlife and dies honorably.

Trivia

 * Prior to Kingdom Hearts 3, he started out as a Pure Evil irredeemable villain who's original goal was to cover the world in darkness and start the Keyblade War out of his own curiosity regardless of how many lives he have to take or ruined.