Some sort of evidence that he'd taken action indication regret, understanding, or a desire to leave the world better off would probably do. Has he? I don't know. I know of people who've done terrible things, and found a way to recover. One of them is a murderer, who was so regretful over what he did that he's dedicated his life to saving lives, and been fairly successful at it, even partnering with the police officer that originally caught him.
I've not heard of this man doing anything to atone for his crimes, or even showing any sort of regret. He may have, and if anyone has any evidence of it, I'd like to see it.