My favourite Korean actor is Yim Siwan. I particularly appreciate how much of his work is murder-y, which makes it easy for me to watch. As opposed to actors I might really like in one thing but then it turns out they've mostly been in romantic dramas :(
The shows I have seen him in are:

If you know me, you might wonder how I managed to sit through a show like Summer Strike, and the answer is:
I have also watched the travel show (Actors on the Road) where Yim Siwan and another actor go to Scotland. They made a big deal about the two of them being the same age (born in 88) and what do you know I also was born in 88??? Same-age friends.
Films of his I have seen: