Do we have Batman? If yes, Tyler Durden. If not, Joker.
Reasoning:
Tyler Durden is a bit mentally unstable, and he does have a knack for building a cult-like following, but he does have a level of grounded thinking. He doesn't believe in big government, but he believes in humanity and self actualization. The Joker, on the other hand, is beyond mentally unstable. He's crossed into psychopathic territory, with no moral boundary to restrict his actions. He is also more resourceful in how he operates (i.e., better explosives). While both characters exude a disregard for their own well-being, The Joker has bigger goals and he is willing to sacrifice more to accomplish them.
But Batman has already proven that he can take him down.
Joker > TD
Batman beats Joker. Joker beats TD. TD beats Batman?