I Saw The Devil (2010)

Cast
Lee Byeong-Heon (이병헌) as Kim Soo-hyeon (김수현)
Choi Min-sik (최민식) as Jang Keyong-cheol (장경철)
Jeon Gook-hwan (전국환) as Squad chief Jang (장 반장)
Cheon Ho-jin (천호진) as Section chief Oh (오 과장)
Oh San-ha (오산하) as Joo-yeon (주연)
Kim Yoon-seo (김윤서) as Se-yeon (세연)


Trailer

Synopsis
Jang Gyeong-cheol is a dangerous psychopath who kills for pleasure. He has committed infernal serial murders in diabolic ways that one cannot even imagine and his victims range from young women to even children. The police have chased him for a long time, but were unable to catch him. One day the daughter of a retired police chief becomes his prey and is found dead in a horrific state. Her fiance Kim Soo-hyeon, a top secret agent, decides to track down the murderer himself. He promises himself that he will do everything in his power to take bloody vengeance against the killer, even if it means that he must become a monster himself.