OK, so it's a far fetched scenario. but just imagine you won a competition or struck some kind of deal with some higher being- so that you could kill one person in the world and noone would ever know it was you. and you could return to your normal life unplagued by your conscience. who would you choose?
you wouldn't have to physically do the killing either if you didn't want to. you could just wish the person's death and it would happen.
some possible nominations to help you along: