[[quoteright:334:http://static.tvtropes.org/pmwiki/pub/images/Isawthedevil_8170.jpg]]
->''"I will kill you when you are in the most pain. When you're in the most pain and shivering out of fear, then I will kill you. That is a real revenge. A real, complete revenge."''

''I Saw the Devil'' is a 2010 Korean {{Revenge}} movie directed by Kim Ji-Woon (''ATaleOfTwoSisters'', ''Film/TheGoodTheBadTheWeird''). It stars Lee Byung-Hun as Kim Soo-Hyun, a government agent who swears to violently avenge the murder of his fiancée. Said crime was commited by Kyung-Chul Jang (Choi Min-Sik), a psychopath to whom kidnapping, raping and murdering young women come as easy as breathing. What ensues is a dangerous cat-and-mouse game in which both men vow to destroy one another's life.
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!!This movie provides examples of the following:

* AgonyOfTheFeet: Kyung-Chul's ''both feet''. [[spoiler:One has its Achilles Tendon cut, another steps on a fishing hook]]
* AntiHero: Soo-Hyun, who doesn't seem to care that his plan for revenge also puts innocent bystanders in danger. [[spoiler: At one point he lets Kyung-Chul rape someone long enough just so he could disrupt his enjoyment that much further.]]
* AttemptedRape
* {{Badass}}: Soo-Hyun, especially during [[spoiler:the fight in the old mansion where he takes out Kyung-Chul and two other serial killers, all of whom were hunting him]].
** Kyung-Chul too, unfortunately. Despite how utterly monstrous and despicable he is, or rather in spite of it, [[spoiler: he is clever enough to figure out that the car he's hitchhiking in is being driven by two killers and proceeds to violently fight and murder them both. ''While the car is still in motion on a snowy road.'' And as soon as he figures out who Soo-Hyun is and why he's terrorizing him, he immediately turns his revenge plot on its head.]]
* [[spoiler:BittersweetEnding: Soo-Hyun manages to murder Kyung-Chul, but then he realizes [[HeWhoFightsMonsters what he's become.]]]]
* BottomlessMagazines: A mild case when Kyung-Chul shoots three times with a double barrel shotgun before reloading.
* {{Bowdlerized}}: The Korean version was effectively censored by the Korea Media Rating Board; several shots of violence and some scenes depicting cannibalism had to be removed before being released. The international version is uncut and true to the director's intentions, however.
* CowboyCop: Soo-Hyun.
* CurbstompBattle: Kyung-Chul is very skillfully beaten whenever he engages Soo-Hyun in hand-to-hand combat. Justified in that Soo-Hyun is a trained government operative.
* {{Determinator}}: Soo-hyun[[spoiler:, but not as much as Kyung-Chul]]. To elaborate, [[spoiler:, Kyung-Chul gets into a car accident and breaks his arm. Later he has the tendons in one of his foot cut. Not long after his head is bashed in with a pipe. Through all of this, he is still somehow able to inflict brutal, murder when in any normal situation he could have been defeated by being shoved to the ground and kicked.]]
* DevilInPlainSight: How Soo-hyun sees Kyung-Chul. The title, which explains it all, is considered an ironic coincidence.
* DisposableWoman: Joo-Yun.
* ExecutiveMeddling: See {{Bowdlerized}}.
* FilmNoir
* FromBadToWorse
* GlasgowGrin: [[spoiler: Soo-Hyun gives this to one of the cannibals by ripping open his mouth with his bare hands.]] We only see it briefly.
* {{Gorn}}: Oh boy.
* HeWhoFightsMonsters: Explored and discussed.
* HypocriticalHumor: Kyung-Chul often calls everyone crazy and/or psycho.
* IdiotBall: The Police has it bad. They have called Kyung-Chul in before, and know where he lives. So [[spoiler: When Kyung-Chul left all his evidence at the crime scene at the start of the movie, why didn't they get him then?]]
* ImAHumanitarian: Kyung-Chul is friends with some cannibals.
* InfantImmortality: Just about the first thing the film does is subvert this.
* JackBauerInterrogationTechnique: Soo-Hyun uses this on some suspects early on when he's looking for the killer.
* ManlyTears: At the end, [[spoiler:Soo-Hyun breaks down crying after finally killing Kyung-Chul]].
* NotIfTheyEnjoyedItRationalization: A scene only available in the Korean version of the film (the director cut it out of the international version for pacing reasons) has Kyung-Chul raping his cannibal friend's wife only her for to enjoy it after a while.
* OvertOperative: Soo-Hyun
* ParentalAbandonment: Kyung-Chul has a son whom he left with his parents.
* PayEvilUntoEvil: Soo-Hyun's vow.
--> ''I'll promise this. I'll give him pain that's 1,000 times... no, 10,000 times more painful.''
* [[spoiler:TheKillerBecomesTheKilled]]
* {{Revenge}}:
** RevengeBeforeReason: What eventually defines Soo-Hyun.
* SacrificialLamb: Joo-Yun, whose death at the hands of Kyung-Chul kicks off the plot.
* SerialKiller: Kyung-Chul.
* [[spoiler:SerialKillerKiller]]: Soo-Hyun
* ShoutOut: Kyung-Chul ends up in a situation straight from ''Film/BloodsuckingFreaks'': [[spoiler: in a guillotine, holding the blade up with his teeth]].
* SmallNameBigEgo: Kyung-Chul. Even though he's a sleazy serial killer whose only known "friend" is [[spoiler: a psychotic cannibal]], he thinks very highly of himself. [[spoiler: And doesn't change his tune until the moment he is brutally killed.]]
* TooDumbToLive: Averted. Joo-Yun quickly realizes there's something strange about the man offering to help her with her flat tire, declines his help, and rolls up her windows and locks her doors. [[spoiler: It doesn't save her.]]
* TranquilFury: Soo-Hyun maintains this state throughout the movie.
* UnderestimatingBadassery: Soo-Hyun eventually discovers what a bad idea it is to keep a deranged psychopath alive to toy with.
* VillainousBreakdown: Near the end of the movie [[spoiler:Soo-Hyun succeeds in getting Kyung-Chul to beg for his life like so many of his own victims. Subverted in that it was an act on Kyung-Chul's part]].
** [[spoiler: Then played straight when Soo-hyun leaves and Kyug-Chul's parents and son for earlier come to visit him. Kyung-Chul really starts to panic as they're about to see him in the state Soo-hyon left him in, holding a rope, that released would let the guillotine down, with this teeth]].
* WickedCultured: The Cannibal Tae-joo enjoys listening to classical music while preparing his "meals".
* WhatHappenedToTheMouse: What happened to the schoolgirl and the kidnapped victim in the cannibal's house? Also, [[spoiler: Soo-Hyun's sister-in-law, though {{WordOfGod}} has it that she was killed.]]
* WhatCouldHaveBeen: Featured on the DVD/Blu-Ray is an deleted extension to the ending which [[spoiler: after breaking down due to realizing what he became in the process of getting his revenge against Kyung-Chul]], Soo-Hyun is ordered by his bosses to disappear to China till things quiet down in Korea after what he did. Before he can go to his ferry, he notices a teenaged girl, who was seeing off her friends, walk to an isolated escalator and goes down it with a suspicious, stalker-looking guy following her. After giving it some thought, Soo-Hyun silently heads towards the escalator, hinting that, since he really has nothing left to live for and that he didn't get enough satisfaction from his revenge on Kyung-Chui, he's gonna look for more, accepting being the monster he became and will presumably become an PayEvilUntoEvil style vigilante.
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