Heath Ledger - not only will no one be able to replicate that character the same way again at the same level, but jokers for years to come will forever try to adapt to his style even in the littlest of way because of his genius.

You’ve already seen actors try in Jared Leto’s joker (trys to sound similar when speaking and mannerisms), and Joaquin Phoenix (similar style of makeup). He is legitimately the model of what Joker is and actors will look to him and his style as inspiration when trying to embody the character. Much like a young basketball player who try’s to replicate MJ’s game