InfoDroid said:
Lando's "sin" was selfishness. The only way to fully redeem himself for that is selflessness. The points you mentioned demonstrate some selflessness, yes. But keep in mind the magnitude of his betrayal. Han would never have been frozen or taken to Jabba's "nasty palace" if Lando had made a stand...or even warned him in some way...C-3PO was blasted to pieces, Leia, Chewie, Han and Luke were all lucky they didn't get killed. And if they HAD been killed, there'd be no Vader redemption and the galaxy would never have broken the Emperor's grip.

What he did was baaaadddd....

Thats where we have to disagree. I think Lando's mistake was trusting the Empire. He was forced to weigh the wellbeing of Cloud City against one man's life (Luke's. If you recall, giving Han to the bounty hunter was never part of the bargain). You can see why he felt he 'had no choice.'

When he sees the Empire isn't playing square, he sacrifices everything he has and risks his life to try to make up for that one mistake.

I don't think he was selfish at all, and I disagree he has anything further to atone for.