Summer's Desire and Lee Jun Kai. Both have really intense-bordeline-agressive-possessive-jealous scenes. Peter Ho do knows how to play psychotic/obsessive characters!
Que Sera Sera. Really intense jealousy. With an almost-rape like scene. It's a dark drama overall. But Eric Moon is mouthwatering. And the theme song is just amazing.
My Lovely Kim Sam Soon. Male lead choose ex-girlfriend over female lead. Boy, do he regreat it! Specially when the female lead starts to go out in dates and meet her ex (even though he is a jerk). By the way, the heroine is considered ugly and chubby for the absurd korean standard, so is even more sweet when he starts pining for her.
Goong. Pretty classic drama. Backstabbing cousin falls for the heir's (to the trone in an alternative Korea) wife. He was the original heir, but because of odd political issues, he feels like his younger cousin robbed him the trone. Wich he kind of did, involuntary. Anyway, both fall for the same girl who has an arranged marriage with the younger cousin and future king.
Mary Stayed Out All Night has a few jealous-scenes. Male lead even throws a punch. Huge second male sindrome in this one. Female lead is just too cut, without being overly annoying - definitely a pro! Killer OST!