Wook was such an insolent brat *spoilers*
I really loathed his character wholly. There was not one redeeming scene for him in the entire movie. I understand this was obviously the director's intent but it really sickened me how he thought he and his friends could just continually rape a classmate until she is driven to kill herself and then everything would just be alright. Probably one of the most repulsive characters I've seen in any movie as of late. Perhaps I am overreacting but I felt kind of angry whenever his face would appear on the screen.
I thought that he would get away with it at the end, which I am so glad didn't happen. It's really such a great, great (albeit sad) ending. Ultimately the poor grandmother ended up taking he and his friends actions to her grave. The main actress did such a fabulous job. Kudos to her!