I'd rather like to see something like a redemption : I hardly ever see in games, movies, books etc. that a deeply evil character becomes redeemed - a bit like Darth Vader in the end (Or Kam Solusar, if anybody knows who I mean).
But - this rdemption shouldn't be without a price. The formerly evil person should have to suffer from his or her evil deeds of the past ... Inclusive heavy doubt, and a nearly broken character (which should need a psychotherapy in real life), deeply, rich character who's "redeemed", but always wished he or she hadn't done what he or she actually did.
I don't know how I could illustrate it much better, but I do hope that you get my idea.
I'm not sure, but I think the sorcerer (?) you free in the mines of Nashkell (BG1) goes into that direction, looking as weak and whining, although he's in fact a very powerful character - if he would see it. The only difference is that this one in BG1 is a good character from the start.
The redeemed evil character should act and reflect like havoing a rollercoaster ride behind him: First, he believed in everything to be "right" when he or she was evil, and then learns that everything was "wrong", and he or she (with females I think it might even be stronger, because it breaks so many clichés), and killed so many people he or she in a way cared for, destroyed the environment (like a Druid realising that he scorches his Mother Earth when he thought he was "on the right trip") and did things that heavily weightens his or her sould and peace of mind down.
I think this character shouldn't be crazy, or heavily mentally disturbed, but I rather believe that this character should've become depressive in a way - the burden of the many lives he or she has killed before - and sees hope only in trying to do something good, like fighting for the evil he or she once incarnated, and saving as many lves as possible through this.
Although in my chracterization this character shouldn't be crazy or mad, I think that this person should need constant encourage, because of this almost too heavy burden (a bit like Hamlet, I think this could be a good choice).
Not like ... who was the one who carried Boo with him ? I've forgot his name ... Minsc, I think was it. No, this character shouldn't be like Minsc, because this would be too far on the "mentally disturbed" lane, but rather like Hamlet, maybe.
Plus - what might make his or her tragedy even worse - that this character constantly has an Aura of Hope around him or her (like a Paladin, perhaps), and people constantly ask him or her for help - even close friends or relatives of those he or she had murdered before.
Having to face the relatives and friens of those he or she murdered before ... - and be confronted with the constand memory and tragedy of his or her former deeds ...
