Con Carne said:
If by chance Hitler was still alive, or if he just happened to come back from the dead. He calls a world wide press conference, admits to guilt, says he's deeply sorry, regrets all that he has done and is asking for forgiveness. He says he will do anything to redeem himself and asks for suggestions. You are in the front row of his press conference, and he points to you for the first suggestion. Do you tell him to kill himself, or do you think of something else?
Well, trust would be an issue. Hitler is a massively charismatic guy. The scary thing about him isn't that he was a genocidal mass murderer, but that he was right about 99.9% of everything he said and believed, so that 00.01% of it kind of snuck up on you, and seemed reasonable to a lot of people when it eventually did show up.
He's the kind of guy where I'd think if he was right there, he might be able to convince a lot of people to give him a second chance and well... how can you trust him?
If somehow you could verify his sincerity, then I'd probably put him to work on trying to fix the global economy. It would be a sign that he overcame his insanities, and really killing him would probably wind up accomplishing nothing... say all you want about revenge.
That's kind of a moot point though, because I don't think the sincere reform of Adolf Hitler could ever be proven to my satisfaction. In every single thing he did, I'd be looking for where it could go wrong, and I'd be wary of anyone who didn't look at him under that magnifying glass.
I guess the most fair way to deal with the situation, and to see if he was sincere, was to request he go to Isreal to answer for his crimes to them. If the Isrealis believe in his reform and are willing to let him go under THOSE circumstances... well, as I said, I think the guy probably has one of the finest economic minds in history.