I Saw The Devil
After his fiance is murdered, a secret agent decides to track down and take vengence against the killer.
Kyung-chul (Choi Min-sik, Oldboy) is a dangerous psychopath who kills for pleasure. He has committed infernal serial murders in diabolic ways that one cannot even begin to imagine and his victims range from young women to even children. The police have been chasing him for a long time, unable to catch him, until one day, Ju-yeon, daughter of a retired police chief, becomes his prey and is found dead in a horrific state. Her fiancé Soo-hyun (Lee Byung-hun, A Bittersweet Life), a top-secret agent, decides to track down the murderer himself. He vows to do everything in his power to take bloody vengeance against the killer, even if that means he must become a monster himself.