[[quoteright:334:https://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 South Korean {{revenge}} action thriller film directed by Kim Ji-woon (''Film/ATaleOfTwoSisters'', ''Film/TheGoodTheBadTheWeird'', ''Film/ABittersweetLife'') and starring Creator/LeeByunghun and Choi Min-sik.

After his fiancée is horrifically and indiscriminately murdered, government agent [[AntiHero Kim Soo-hyun]] (Byung-hun) vows to avenge the murder by any means necessary. He eventually finds the killer in [[BigBad Jang Kyung-chul]] (Min-sik), a psychopath to whom kidnapping, raping and murdering young women come as easy as breathing.

Considering [[ItsPersonal how close to home his offense is]], Soo-hyun decides to [[CowboyCop take matters into his own hands]] in regards to giving Kyung-chul what he deserves. What ensues is a cat-and-mouse game in which both men vow to destroy the other's life, and while Kyung-chul isn't willing to give up the last laugh without a fight, Soo-hyun runs the risk of [[HeWhoFightsMonsters giving in more and more to his darkest desires]]...
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!!This movie provides examples of the following:

* AgonyOfTheFeet: Both of Kyung-chul's feet. [[spoiler:One has its Achilles tendon cut, another steps on a fishing hook.]]
* AintTooProudToBeg: Double subverted. [[spoiler:When Soo-hyun finally gets Kyung-chul exactly where he wants him to execute his final act of revenge, Kyung-chul seemingly breaks down and begs for his life. However, he then drops the act and states that he cannot feel pain or fear -- the exact things Soo-hyun wants him to feel the most -- and so Soo-hyun's work is AllForNothing. However, once he leaves Kyung-chul holding up his own guillotine blade by a rope in his teeth that connects to a door, his family arrives and starts to open the same door, at which point he begins letting out very real, very terrified pleas for them to leave. [[HoistByHisOwnPetard It]] [[OffWithThisHead doesn't boot.]]]]
* 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.]]
* AssholeVictim: The two crooks in the taxi plan to rob and kill Kyung-chul, who figures it out and kills them both.
%%* AttemptedRape
* AxCrazy: Kyung-chul reveals himself to be a danger to just about everyone around him. Even after getting his hand mended by a doctor, he nearly decides to murder the doctor over some gentle scolding. The only reason he relents is because he turns his attention on the doctor's attractive nurse. All of this is part of what makes Soo-hyun's catch-and-release plan so reckless.
* BigBad: Kyung-chul is the psychopath whose being at large while committing murderous acts sets the story in motion.
* BlackComedy:
** While preparing to murder a woman he's given a ride, Kyung-chul misplaces his murder weapon. He rummages around behind his seat muttering to himself while his future victim watches him in confusion.
** When Tae-joo tries to remove the screwdriver pinning his hand on the table, the handle promptly comes off with a humorous "pop!" He slams the table in frustration.
* BookEnds: The film's main plot begins and ends with [[spoiler:the discovery of a head]]. At the start it's [[spoiler:Joo-yun's, as discovered by the police, severed by Kyung-chul]], and at the end it's [[spoiler:Kyung-chul's, as discovered by [[KickTheDog his own family]], severed by a trap set up by Soo-hyun]].
* BottomlessMagazines: A mild case when Kyung-chul [[spoiler:shoots at Soo-hyun three times with a double barrel shotgun before reloading]].
* {{Bowdlerise}}: 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.
* CaughtWithYourPantsDown: When Soo-hyun drops in on his first suspect, he's busy masturbating to porn in his room. He decides to alert the suspect of his presence by cutting his computer's power just as he's about to finish.
* ChekhovsGun: Joo-yun's ring. [[spoiler:It falls in a nearby gutter as Kyung-chul dismembers her, and Soo-hyun digging in and finding it later is what makes him realize Kyung-chul has killed her.]]
* CowboyCop: Deconstructed with Soo-hyun. Considering [[ItsPersonal Kyung-chul has killed his greatest love]], [[JustifiedTrope it makes sense that he'd have zero interest in waiting for the cops to get things done, and want to get hands-on.]] [[spoiler:The problem comes in [[HeWhoFightsMonsters just how dirty he's willing to get his hands]] to see to his own personal sense of justice. In his decision to drag out his retribution, he allows more murders and rapes to happen, and come the end of the film, his superiors are ''furious'' with him, and his victory is too costly to enjoy anyway.]]
* CurbStompBattle: Justified; since Soo-hyun is a trained government operative, he wins every close-range fight he enters without much hassle.
* {{Determinator}}: Soo-hyun, [[spoiler:but not as much as Kyung-chul]]. To elaborate, [[spoiler: Kyung-chul gets into a car accident (after murdering the two people inside the car with him) and breaks his arm. Later, he has the Achilles tendon in one of his feet 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 [[DoubleMeaningTitle an ironic coincidence]] in that [[spoiler:his sadistic acts turn him into a Devil-like figure himself come the end]].
* DisposableWoman: Joo-yun, whose death kicks off the plot.
* DownerEnding: [[spoiler:Soo-hyun manages to see to the end of his retribution against Kyung-chul, resulting in his death, but by this point, it's clear he's lost everything. His career as a police officer is in jeopardy because of the sheer amount of damage he's caused in his pursuit of vengeance, his father-in-law ends up grievously injured, his sister-in-law ends up killed, and in having Kyung-chul decapitated [[KickTheDog right in front of his parents and son]], Soo-hyun realizes that [[HeWhoFightsMonsters he has become just as monstrous as Kyung-chul had been]]. By the end of the movie, he's walking away from all the carnage he's caused, crying hysterically, completely alone.]]
* EvenEvilHasLovedOnes: Tae-joo the cannibal has a girlfriend, though their relationship isn't explored. It's not even clear if she's a cannibal as well, since she scowls at him when he's eating human flesh and is only seen eating rice herself.
* EvenEvilHasStandards: As psychotically depraved as Kyung-chul is, he’s unnerved by Tae-joo’s acts of cannibalism. He may be a sadistic rapist and murderer, but he draws the line at eating people.
* EvilVsEvil: By the end of the film, [[spoiler:Soo-hyun's desire for revenge has made him just as monstrous as Kyung-chul.]]
* FarEastAsianTerrorists: It’s implied that this is how Tae-joo and Kyung-chul know each other. Tae-joo mentions that the two of them were in a “militia” movement and wanted to cause chaos throughout the world. It’s certainly a reasonable explanation for how two very depraved people came to be friends.
* 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.
-->"Funny? Is that really funny? That really makes you smile? Alright, I'll make you smile for the rest of your life."
* GoodSmokingEvilSmoking: Smoking is treated as villainous.
** Squad Chief Jang smokes while in mourning for his daughter. Soo-hyun gently tells him he should stop.
** Kyung-chul is constantly seen smoking.
** In the end, [[spoiler: Soo-hyun smokes a cigarette and uses it to burn Kyung-chul]].
* {{Gorn}}: The film ''opens'' with [[spoiler:a brutal bludgeoning and dismemberment]] and doesn't really ease up on the gore from there.
* GroinAttack: Soo-hyun ends up smashing his first suspect's groin repeatedly with a hammer.
* GrossUpCloseUp: Some of the film's most violent acts are depicted in close, excruciating detail (ex: [[spoiler:Soo-hyun bludgeoning a man's genitals]], [[spoiler:Soo-hyun severing Kyung-chul's Achilles tendon]]).
* HeWhoFightsMonsters: Essentially the core of the film, as it's explored in Soo-hyun's increasingly sadistic persistence in exacting revenge against Kyung-chul, as well as {{discussed|Trope}} by other cops [[LampshadeHanging commenting on his behavior]].
* HoistByHisOwnPetard: [[spoiler:One of Kyung-chul's preferred murder types is decapitation via guillotine; he is ultimately offed in that fashion by that same blade, in a particularly twisted setup organized by Soo-hyun. He's left holding between his teeth a rope which connects to a door and then up to the blade. When his family arrives later, they inadvertently trigger his decapitation by opening that door and pulling the rope out of his teeth.]]
* HypocriticalHumor: Kyung-chul often calls everyone "crazy" and/or "psycho."
* IdiotBall: The police have it bad. They have called in Kyung-chul before and know where he lives. So [[spoiler: when Kyung-chul leaves all his evidence at the crime scene at the start of the movie, why didn't they get him then?]]
* ImAHumanitarian: Tae-joo is a cannibal, declaring that you'll never want to eat anything else after you taste human meat. He noisily scarfs down bite after bite during dinner with Kyung-chul.
* InelegantBlubbering: At the end, [[spoiler:Soo-hyun breaks down crying after finally killing Kyung-chul]].
* JackBauerInterrogationTechnique: Soo-hyun uses this on some suspects early on when he's looking for the killer.
* {{Jerkass}}: Aside from the whole SerialKiller business, Kyung-chul treats every last person he comes across with violence, hostility and contempt -- and that's when he doesn't end up killing them.
* JumpScare: The [[BookEnds first and last]] times Kyung-chul attacks a woman, it's played out like this.
* TheKillerBecomesTheKilled: [[spoiler:Kyung-chul is ultimately murdered by Soo-hyun.]]
* LonelyPianoPiece: Soo-hyun's theme, used to full effect over the film's closing shot: [[spoiler:him sobbing, alone in the middle of the street, having lost everything in his mission. The camera even pulls back at the very end to make him smaller and more isolated.]]
* MuggingTheMonster: The two crooks in the taxi plan to rob and kill Kyung-chul, not knowing he is a murderous psychopath. It ends about as well as you'd expect.
* MyGodWhatHaveIDone: The most likely reasoning behind [[spoiler:Soo-hyun's breakdown at the end of the film, in combination with his loss and all the lives he indirectly ended or changed forever]].
* NiceJobBreakingItHero: Soo-hyun's constant catch-and-release torment of Kyung-chul results in [[spoiler:the latter committing more murders and rapes, eventually finding out Soo-hyun's identity, tracking down Joo-yun's family, beating her father within a centimeter of his life, and killing his sister outright]].
* NominalHero: Soo-hyun is only interested in [[PayEvilUntoEvil avenging his fiance's murder]] [[RevengeBeforeReason above all else]].
* 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 [[spoiler: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. [[spoiler:He ultimately makes good on it, and [[PyrrhicVictory he couldn't be less happy about it]].]]
-->"I'll promise this. I'll give him pain that's 1,000 times... no, 10,000 times more painful."
* ProtagonistJourneyToVillain: Soo-hyun begins the film as a sympathetic antihero motivated by getting vengeance on a brutal murderer. [[spoiler:He makes more and more moral concessions to his vengeance, until, by the end, he's completely sacrificed his humanity.]]
* PyrrhicVictory: [[spoiler:Soo-hyun may have gotten his revenge by murdering Kyung-chul, but he ends up causing huge amounts of damage, including his father-in-law being grievously injured and his sister-in-law being killed. Never mind the fact that he also [[HeWhoFightsMonsters becomes]] [[EvilVsEvil just as monstrous as Kyung-chul was in his pursuit for vengeance.]]]]
* RasputinianDeath: [[spoiler:Kyung-chul survives a lot of serious injuries at the hands of Soo-hyun before his guillotine finally does him in -- namely being beaten unconscious, having his wrist broken, losing several fistfights and cracking a couple bones in the process, taking a fire extinguisher multiple times to the face, getting his Achilles tendon severed, getting his head split open with a rod, taking a hot cigarette to the face, and being impaled through the cheeks.]]
* {{Revenge}}: Soo-hyun and his would-be father-in-law are motivated by vengeance against the murder of Joo-yun.
* RevengeBeforeReason: Soo-hyun strives for revenge over all other factors, even after being begged to stop by his fiance's family and his boss, and even though it puts a number of other people in grave peril.
* RuleOfDrama: There's no given reason why Kyung-chul's sedatives wear off nearly a day earlier than expected, just in time to make a critical discovery [[spoiler:(Soo-hyun's planted a tracker in him)]]. It happens simply to drive the next plot point.
* SacrificialLamb: Joo-yun, whose death at the hands of Kyung-chul kicks off the plot.
* SayingTooMuch: While talking with Soo-hyun, Squad Chief Jang makes the [[UnwittingInstigatorOfDoom fatal error]] of [[spoiler:bringing up the TrackingDevice Soo-hyun planted in a nearby Kyung-chul ''and'' the only way to get rid of it just as his sedative wears off]].
* SerialKiller: Kyung-chul has killed around a dozen women, as evidenced by the trophies in his lair, and always after raping them, as pointed out by Tae-joo.
* SerialKillerKiller: [[spoiler: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]].
* SickeningCrunch: Soo-hyun breaks a fair share of his opponent's bones [[spoiler:(Kyung-chul and Tae-joo)]] during his hand-to-hand fights.
* 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 and [[spoiler:doesn't change his tune until the moment before he is brutally killed.]]
* SoftGlass: Averted. Soo-hyun knows that this is not true. The only time he jumps through a window, he wears gloves and a rather thick hoodie, and also grabs a sheet of cloth for extra protection.
* SoundtrackDissonance: Tae-joo prefers the sound of [[Theatre/{{Carmen}} "Habanera"]] when dismembering his victims.
* StupidCrooks: The killers in the film are hardly masterminds.
** Kyung-chul misplaces objects a few times, coming across as fairly bumbling on occasion.
** Tae-joo knows that a merciless SerialKillerKiller is hunting his house guest, but takes no precautions. When his CD player spontaneously shuts off, he doesn't display any awareness that there might be someone skulking about. He even fumbles with the controls trying to turn it back on.
* TearsOfRemorse: Soo-hyun sheds these at the end. While probably not regretting [[spoiler:killing Kyung-chul]], he probably regrets [[spoiler:the things he did to get Kyung to where he wanted him and that he's become just as bad as he is]]. But by the time he realizes that it is too little, too late.
* TooDumbToLive: A woman standing at a deserted bus stop at night lets herself get convinced to accept a ride from a very insistent stranger in a van. She ''does'' hesitate quite formidably, but ultimately caves. [[spoiler:She is killed for it.]] Justified, however, because he convinces her that the bus has stopped running for the night and that she'll be stranded otherwise.
* TrackingDevice: Early in the film, Soo-hyun gets a transmitter from his agency that tracks GPS location and acts as a microphone. [[spoiler:He shoves it down Kyung-chul's throat and uses it to listen to his conversations and find him when he's committing heinous acts; however, he eventually finds out about it and eats laxatives to rid himself of it.]]
** A more minor example is [[spoiler:the transmitter he plants on the school van Kyung-chul drives for similar purposes]].
* TranquilFury: Soo-hyun maintains this state throughout the movie.
* UnderestimatingBadassery: Soo-hyun eventually [[DidntThinkThisThrough discovers what a bad idea it is to keep a murderous psychopath alive to toy with]].
* VillainousBreakdown:
** Near the end of the movie, [[spoiler:Soo-hyun succeeds in getting Kyung-chul to [[AintTooProudToBeg beg for his life like so many of his own victims]]. Subverted in that it's all an act on Kyung-chul's part]].
** [[spoiler:Then played straight when Soo-hyun leaves and Kyung-chul's parents and son come to visit him. Kyung-chul really starts to panic as they're about to see him in the state Soo-hyun left him in, holding a rope with his teeth that, if released, will release a guillotine's blade hanging just above him]].
* VillainsOutShopping: An early sequence has Kyung-chul engaged in mundane activities such as preening his hair and playing acoustic guitar.
* 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? We see them scurry away as Soo-hyun battles Kyung-chul, but there's no follow-up. One can presume that the police took care of the latter.
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