Originally Posted by Iron Ape
Obvious recommendations, but: I Saw The Devil is pretty much a must-see for you. And while it's not a revenge-flick, so is Chan-wook's earlier film Joint Security Area. (which I actually enjoyed *more* than the Vengeance trilogy, except maybe Lady Vengeance)
Thinking about Korean cinema just reminded me to watch everything Lee Chang-Dong ever directed. Peppermint Candy is such an incredible piece of filmmaking.
Black God, White Devil (1964) - 9/10
Killer of Sheep (1977) - 8/10 - This whole "Story of Film season" on More 4/Film 4 is amazing. There's been loads of really incredible art films on TV this past couple of months (as well as tons of Pedro Almodovar and Ken Loach films, which may or may not be related)