Why Do We Love a Good Redemption Story?

Can anybody become the good guy? We love a good redemption story. Darth Vader, Zuko, Loki, Nebula, Bucky Barnes and countless others have gone from villain, rival, or deeply broken person to someone we're rooting for. But what actually makes a redemption arc work? Is feeling sorry enough? Does the character have to make restitution? And are there some things a character simply can't come back from? Plus an update on the crew, who is leaving the show this season (and why?) and our latest BEST THING EVER!