1. "I Saw The Devil" makes every revenge thriller I've seen in years look like "Bride Wars." It is brutal, unrelenting, terrifying and, to be frank, disgusting. We love our film heroes to be bent on revenge, but in an understandable way, motivated by vengeance but ultimately subject to reason and the acceptance that even if their bloodlust is sated, it won't bring back the person they lost. "I Saw The Devil" turns this on its head. It forces us to follow vengeance to its logical conclusion. This is not a "at what cost?" revenge thriller. This is a "my pain is so strong that I must destroy everything" slasher flick. Our wronged hero wants to eviscerate the cause of his suffering. He also wants to eviscerate everything else.
2. The opening scene of "I Saw The Devil" is so skillfully horrific that you'll think the rest of the movie can't possibly measure up. You will be wrong. A woman's car breaks down, and she talks to her fiance Soo-Hyun (Lee Byung-hun) on her phone while she waits for a tow truck. Out of nowhere, a drifter, played by "Oldboy"'s Choi Min-sik, shows up to "help." That help involves the man, Kyung-Chul, sexually assaulting the woman, murdering her and chopping off all of her limbs. This is a delightful romp compared to what happens the rest of the film. Director Kim Ji-woon stages this with considerable craft and impressively alternates between precision and showiness: This is a film that is not messing around.
3. Soo-Hyun, a special forces officer in the Charles Bronson mode, vows to track down Kyun-Chul, and it's a surprise when he finds him just 45 minutes into the film's 2 1/2 hour running time. The film is just getting started. Driven by rage, Soo-Hyun plays cat-and-mouse with Kyun-Chul, torturing him to the point of death, and then releasing him so that he might prolong the misery. We get a succession of breathtakingly violent scenes, but we notice something that Soo-Hyun does not: Every time he lets Kyun-Chul go, Kyun-Chul gets a little bit smarter and little bit deadlier. Soo-Hyun believes he is giving Kyun-Chul the horrific, extended, painful death he deserves. But Kyun-Chul finds himself liberated by this sudden game and begins to even enjoy it. And there are plenty of people caught in the crossfire. Soo-Hyun wanted revenge, but he ends up causing more misery to more people, including those he cares about, than he ever could have anticipated. But the film's cosmic joke is that, all told, you don't get a sense he minds that much. He just wants pain, ultimately in the same sick way Kyun-Chul does.
4. The center of the film is Choi Min-sik's performance, which is an exhiliarating combination of Heath Ledger as The Joker and Ted Levine as Jame Gumb. He is a vessel of pure evil and chaos, a man who cannot be reasoned with or talked down: He wants to kill, rape and maim everyone in his path, without ever pausing to ask why or think all that much about it. But he's also a vain, sloppy, wimpering man who, for the God complex that allows him to justify his evil, still just wants to survive so he can keep killing. Choi Min-sik is outstanding, his stringy, oft-bloody hair flapping everywhere, madness surrounding and engulfing him. For this film to reach the depths it's willing to go, it needs a "devil" to fully commit to the insanity. Choi Min-sik is more than up to the task.
5. This is not a movie that wrings its hands about the morality of revenge, or its ultimate countereffects. Soo-Hyun's decisions cost many people their lives, in awful, awful ways, but the movie is agnostic as to whether or not he should feel horrible about it. That is: He should, but that's not what this movie is about. This movie is about madness and sickness, about two men locked in a vicious, grisly battle, the rest of the world be damned. It's a terrific thriller, muscularly directed and unflinchingly observed, punishing and painful to witness. This film, with its extended scenes of violence, assault and pain, drags you through the mire every step. It's not fun, but you can't say it ever cheats. It's a terrible time at the movies, and for that it is truly quite great. But you've been warned.