J'ai rencontré le Diable (2010)

Brutal South Korean film about a serial rapist/killer (Min-sik Choi, Oldboy) who picks on the wrong girl when he kills and chops up the pregnant fiancee of a government secret agent (Byung-hun Lee, A Bittersweet Life, The Good, The Bad, The Weird) who proceeds to track him down, beat him to a pulp, place a tracking device on him, give him some money and release him. The idea being that he wants the killer to suffer and suffer and suffer, again and again, until his fear is as great as that of his victims, before he kills him.

I Saw The Devil is not without its faults; at almost two-and-a-half hours, it's too long, the brutal nature of the characters threatens to slide into absurdity especially when our killer takes refuge with a cannibalistic mate who doesn't mind his wife being raped (she doesn't mind, either; I guess your standards slip when your old man eats people for shits & giggles), and the concept of getting this serial rapist/killer to a point of sheer terror, like his victims - is flawed; this guy, as played by Min-sik Choi, is NEVER going to feel any fear. And so it is, by the end, rendering the whole catch/release premise redundant. That said, it's gripping, it's tense throughout much of the runtime, the lead performances are superb, it's astonishingly violent and gory, but it's meted out just right; more Seven than Saw, and it is photographed exquisitely. A serial killer movie bordering on torture porn, set in Korea in the snow, shouldn't logically have a colour palette this vivid, but every frame is just beautiful.