Star Wars: Every Sith Who Turned To The Light Side

Throughout the RPG video game, Star Wars: Knights of the Old Republic, you play as a Jedi who scours the galaxy, looking for an elusive Dark Force user called Darth Revan. Revan was a Jedi Knight who abandoned the Order to found the Sith Empire.

About halfway through the game, the player discovers the shocking twist - you are playing as Darth Revan. After Revan suffered amnesia, the other Jedi pretended he was affiliated with them to convince him to destroy the evil Empire, oblivious to the fact that he was the one who created it.

Depending on the decisions you make in KOTOR, Revan can fully redeem himself and become a Jedi or embrace the Dark Side once again and rejoin the Sith. But according to The New Essential Chronology, Revan was canonically considered a redeemed Jedi at time of his death.