6. John Wayne (The Conqueror)
John Wayne built his cinematic legacy on playing cowboy tough guys but in 1956 Wayne decided to stretch his acting muscle by conquering the role of a lifetime: the Mongolian emperor Genghis Khan. Wayne lobbied for the role after reading the script and, with Wayne being at the height of his popularity at the time, producer Howard Hughes agreed to cast him as the star. Despite a strong cast, the film was universally panned upon its release with many critics citing the bizarre choice of casting Wayne in the role of the Mongolian warlord as the reason the film fared so poorly. The Conqueror went on to be considered one of the worst films of all time and is listed in The Official Razzie Movie Guide as one of The 100 Most Enjoyably Bad Movies Ever Made. While it's uncertain whether any actor could have saved The Conqueror, Wayne's miscasting ensured its infamy will live on forever.