Providence said
As far as your character concept - I'd like to know a bit more. How does he go about doing this? Let's say it's a spirit - how does he trick it? Or, if it's a curse set in motion, I'm not entirely sure how he would stop it in this manner - as much as he'd be capable in in breaking a curse, I don't think he could turn it against itself. If it's a demon, I kind of get what you mean though.
That's why I asked about supernatural entities being shaped by belief. If he can alter the perceptions and beliefs of the people from which the being draws its power, he can alter the nature of the being. Though mindless entities and phenomena, such as curses, are simply not his strong suit. As I said, he specializes in fakes, frauds, phonies and impostors, and is skilled in the art of deception. That about covers his entire skillset. Really, he's more adept at inflicting curses than resolving them.