What are the kdramas that you think are fast paced? I think I like cliffhangers to some level. 

Although the term fast paced might be subjective, here I refer to below kdramas as fast paced in my personal (biased) opinion. May be some persons might find below useful. I also favour drams with leads as cops/detectives/investigators/similar.

Stranger1

Tunnel

Rookie cops*

Chimera

City Hunter*

Healer*

Watcher

(I will add more as I remember here. In above list the stared * are the ones that I'm watching / rewatching)