Keanu Reeves
Keanu Reeves made waves with his performance in Speed. Unfortunately, he wasn't a fan of his own work and refused to be a part of Speed 2. He played Jack Traven, the main character who was tasked with keeping a city bus from going under 50 mph. Otherwise, it would explode.
It's interesting that he did not want to resign for the sequel considering his co-star, Sandra Bullock, did. Instead, Lost Boys star Jason Patric took over as the male lead. Speed 2 was a total flop, and Reeves saw it coming from a mile away.