8. Hayden Christensen (Star Wars: Attack Of The Clones & Revenge Of The Sith)
While George Lucas' trilogy of prequels to his beloved Star Wars film series had a plethora of problems, one of the largest issues with Attack of the Clones and Revenge of the Sith was Lucas' decision to cast sentient fence post Hayden Christensen as the Jedi who would become Darth Vader. Although it's debatable whether any actor could have saved Lucas' misbegotten prequels from being terrible, hiring a competent actor as the central protagonist would have helped immensely. Christensen portrayed the early incarnation of one of cinema's greatest villains as alternately wooden and petulant, failing to bring the gravitas and menace necessary for the role. Some critics derided Christensen's performance and his turns in Attack of the Clones and Revenge of the Sith won him two Golden Raspberry Awards for Worst Supporting Actor. Fans will forever speculate how much better the prequels could have been had a better actor landed the role of Anakin Skywalker.