9. American Psycho
American Psycho is one of the most famous psychological horrors not only on this list but to date. It is a 2000 black comedy and of the genre itself, based on the original novel written by Bret Easton Ellis from 1991.
The story, in both the book and film, is told from the perspective of a serial killer named Patrick Bateman (played by Christian Bale) who meticulously plans out his day, plotting psychotic murders along the way whilst hiding behind a façade amongst his friends and co workers. Bateman's goal is to carry out his killings undetected, showing the downfall of his own mind and the corrupt society around him.
This film wins 10/10 for creepiness, as the audience watch Bateman perform murderous acts whilst uncomfortably calm and collected, if not actively delighted with his success. The cast also includes Jared Leto and William Defoe.
It is not as dark and jump scare filled as the genre typically can be, but captivates viewers with the pure sinister characterisation of the protagonist as he loses his sanity more and more, progressively losing touch with reality altogether.