Heath Ledger in The Dark Knight
Heath Ledger's performance as the Joker in The Dark Knight landed him an Oscar for Best Supporting Actor, but Ledger never got to claim the award. He passed away suddenly in 2008. The actor was only 28 years old.
Ledger pushed himself further than he had ever gone for a role. In the years following his passing, it was speculated that the mental and physical exhaustion of preparing for the role had contributed to Ledger's demise. Members of his family vehemently disagree with this theory—but it's hard to deny that Ledger may have embodied the Joker beyond the point of return.