Which actor performed the best 'Joker'?

@HowtoDestroyAngels yes I read his Joker diary at an exhibition in Canberra. Intense!

@UpForItNow Awesome

@HowtoDestroyAngels I actually went back five times and read it again. Then researched every article about it on the internet. It was my professional role model, that intensity of preparation, locked away for a month alone in a hotel room, getting into character.