muddyknees2000 said:

Whether or not he had a choice is an issue of semantics. His actions bring harm to protagonists = Bad Guy.

I disagree. I think his lack of choice in the matter and the way he handled it all makes him a hero through and through. He never acted out of self interest, but was looking out for everybody the entire time. Sure, the citizens of Cloud City aren't portrayed as characters, but if Lando sacrificed them all to save his buddy and his buddy's girlfriend, I think that would make him a selfish bad guy.
Our heroes (including Han in the next film) seem accept his heroic actions once they realize what he's up to. Even if Han died, Lando did the right thing.