I'd just have you play as a Villain Protagonist. I think I know how that would work though. To summarize a setting lets go with this. Lets go to a medieval Tales like setting (Think Tales of Graces. City of Barona). There will be a coup d' tat. Your protagonist is part of that but he's just a unimportant soldier to the higher ups of the coup. He and four other people enter the castle the day before the coup starts and take most of the treasure but the guards notice when your already done. The other people leave and you attack the guards at your leisure since the king is going to die anyways. You kill the royal family yourself and leave that one traumatized survivor for the heck of it. Your actions took most of the night and by now the coup has started. You meet up with the other people with the money hidden in a carriage and you escape in all the confusion but to really make an opening you had already planted some bombs before the coup had started. So when the countdown finished the castle blows up killing soldiers from both sides and to really reap the reward you take the carriage for yourself and flee like hell.
Is that a new story? The rest is somewhere in my notebook.