Christian Bale's portrayal of the psychopathic murderer Patrick Bateman has become iconic over the years--and for good reason. In American Psycho, a film based on Bret Easton Ellis's novel of the same name, Bateman's off-putting personality and over-the-top reactions in his head are disturbing and yet somewhat believable. However, as a result of his memorably exaggerated performance, Christian Bale decided to model Bateman after a real person to give him some authenticity. Surprisingly, Bale's portrayal wasn't modeled off of a serial killer, but rather fellow movie star Tom Cruise.
Source：https://www.cbr.com/american-psycho-tom-cruise-inspiration-behind-patrick-bateman/
