I Saw the Devil (2010)

Kyung-chul is a dangerous psychopath who kills for pleasure. 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 vengeance against the killer, even if it means that he must become a monster himself.

I Saw the Devil keeps every mind human — it fights its subject at zero distance. The story fights on E8/E9 of the E0–E14 reality ladder.