Memory Lost -the main villain is as yandere as you can get and will go down as one of my favorite yandere males (love big bads who's only weakness is the heroine) -my heart completely ached for him even though I also loved the male lead
One of the latest Kdramas Love in Sadness has a guy who is quite yanderific. He just wouldn't let the main girl go and hunts her down when she leaves. Beware he is abusive too.