This is a quite well known novel, but who knows, maybe you haven't read it.
Warlock of the Magus World
One of the best goal/benefit oriented mc's out there. I would say he is the calculating intelligent type of psychopath. He won't go out of his way to bring harm, but he can do anything and everything at other's expense so long as it is beneficial to him. There is no bottom line, a very selfish and cruel person whose priorities will always be himself. He isn't a complete asshole tho, he does return favors to those who have helped him if he can, but can just as easily abandon them if it's beyond his capacity or harmful to him.