4. ROBERT DOWNEY JR

In the '80s, no one had a brighter future than Robert Downey Jr. Working in films such as Weird Science and Less Than Zero, Downey represented a youth revolution in Hollywood and was touted as one of the best young actors in the biz. But the '90s weren't so kind to Downey. Various drug possession charges were levied against him and he was jailed. One of his drugs of choice? You guessed it: crack.

After dealing with his myriad addictions, Downey went on to make several quality films like A Scanner Darkly, A Guide To Recognizing Your Saints, and Zodiac before owning the summer of 2008 with Tropic Thunder and Iron Man. He proved that, if you're talented enough, a crack addiction in Hollywood can be a mere speed bump on an otherwise nicely paved freeway.