Isaiah Washington
Isaiah Washington was completely banned from working in Hollywood ever again after the blatant homophobia that he presented. On the set of Grey's Anatomy, he referred to a gay coworker by using a slur. He was suspended from his role and attacked the sam coworker again after Grey's won a Golden Globe.
Sondra Locke
Sondra Locke broke into the scene in the '60s. She started dating Clint Eastwood, who was basically Hollywood's Godfather. After their intense breakup, Eastwood made sure that she never started working again. Her entire career was muddled and she was never able to reach the same stardom that she had prior to their relationship because of his blacklisting abilities.