I Saw the Devil is a 2010 South Korean psychological thriller film directed by Kim Jee-woon. The film follows a secret agent whose fiancée is brutally murdered by a psychopathic serial killer. The agent then embarks on a relentless quest for revenge, leading him to a dark
From Wikipedia
I Saw the Devil is a 2010 South Korean action thriller film directed by Kim Jee-woon and written by Park Hoon-jung. Starring Lee Byung-hun and Choi Min-sik, the film follows NIS agent Kim Soo-hyun (Lee), who embarks on a quest for vengeance when his fiancée is brutally murdered by serial killer Jang Kyung-chul (Choi).