I Saw the Devil (2010)

Evil lives inside.

Plot outline

A secret agent exacts revenge on a serial killer through a series of captures and releases.

Plots

A secret agent exacts revenge on a serial killer through a series of captures and releases.

SPOILER: Jang Kyung-chul (Choi Min-sik) is a dangerous psychopath serial killer. 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, Joo-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 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 to get this monstrous and inhumane killer. - jck movies

When Joo-yeon has a flat tire on the snow, she calls the tow truck to help her and calls her beloved fiancé Kim Soo-hyeon, who is a secret agent, to kill time. Out of the blue, a man offers to help her and Joo-yeon refuses. But the man breaks her car, abducts her and dismember her body. Her father, who is a retired chief of police, gives the data of the four prime suspects to Soo-hyeon and he asks two week off to his chief. He hunts the men down and when he finds that Kyung-chul is the killer, he promises a dreadful to revenge against the killer to make him suffer as Joo-yeon did. Soo-hyeon becomes a monster and begins a cat-and-mouse game, capturing and releasing Kyung-chul wounded many times. But the serial-killer is the personification of evil and makes Soo-hyeon regret for not killing him when he had the chance. - Claudio Carvalho, Rio de Janeiro, Brazil

On a dark road, taxi driver Kyung-chul (Min-sik Choi) comes across a scared female motorist stranded in a broken-down vehicle. He pulls over -- but not to help her. When the woman's head is discovered in a local river, her devastated fiancé, Kim Soo-hyeon (Byung-hun Lee), a trained secret agent, becomes obsessed with hunting down her killer. Once he finds Kyung-chul, things get twisted. After brutally beating the murderer, Kim lets him go free, and a demented game of cat and mouse begins. - krmanirethnam