Memories of Murder
I just got through with I SAW THE DEVIL. Good lord.
Then there's the usual suspects like the Vengeance Trilogy (Sympathy for Mr Vengeance, Old Boy, Sympathy for Lady Vengeance).
Even though most of these flicks go over two hours, they're well paced.
I'm sure I'm missing some movies, considering that was just off the top. Someone add to the list.