The story is this. Dae-hoon (played superbly by Byung-hun Lee) is a secret agent whose fiance is brutally murdered and he sets out to find the killer himself. He does so fairly easily. Only instead of killing him, he beats him half to death before making the semi concious killer swallow a tracking device. He then stalks him and exacts his revenge slowly and increasingly more violently. This is about as far from a hollywood slasherfest as you can get. There are no bikini clad girls running about doing stupid things waiting to be killed. This has the type of brutal realism that will make you feel uncomfortable, the type you would expect from a Korean revenge thriller.
What starts out as two totally opposite characters soon blurs the line somewhat as Dae-hoon's actions often lead others into harm as a result of his quest for revenge. His mind has clearly gone a bit due to the pain he is going through and in some scenes you can see how emotionally broke down he has become..However theres no mistaking who the devil is. Min-sik Choi (the lead and star of OldBoy) was brilliant in OldBoy but here he's even better. I dont know if there has ever been a more convincing portrayal of a truly evil, twisted, disgusting, psychopathic rapist killer. Often his facial expressions say more than words ever could. You will probably enjoy every moment of his suffering at the hands of Dae-hoon... The Vengeance Trilogy is tame in comparison.
The acting in particular of the two leads is astounding. The story is great with a few excellent plot twists just when you think one of the characters has the upper hand. There are some amazing scenes, one of the best is a double death that I wont spoil but you will know it when you see it. It's brilliantly done. There are plenty of other stand out moments. Everything is brutal and very realistic, you wont find any over the top kung fu stuff in this and you wont find any of the complexities of the likes of OldBoy either. This is no mystery, it's a very simple straightforward revenge thriller but masterfully done. The ending isn't that original but it is memorable like most of the film, especially the conversation right before the end.
Although banned in Korea on release for "severely damaging the dignity of human values" (and you can see why it would), it's not the most gory or violent film from that region or from the West, far from it, but it is pretty graphic so be warned! There is alot of blood, head bashing with blunt objects, stabbing, and scenes of rape/attempted rape among other things (including a very hard to watch scene with a foot and a knife).
This isnt as intelligent or suspenceful as other korean revenge thrillers and the characters are pretty shallow and one dimensional. I would have liked to have seen a bit of background story on why the killer became who he was. The plot is very far fetched as well but hey it's a film. Just capturing the guy and torturing him wouldn't make much of a film..this does. It also would have been good to see more of Dae-hoons fiances sister just because shes so pretty! Nontheless this is a great film and if you are a fan of korean revenge thrillers or good films in general it's a must. 4/5