I hate mystery dramas unless they have a really good story or plot line.
I love the bromance in dramas like "Hello Monster" & "Strong Woman Do Bong Soon"
but I dislike that one of them will be heart broken:( 
I like idol actors...
I pretty much don't like any female idol actors (although, like you @bahar, I too like a lot of male idol actors!)
I luv to have an element of romance in most of the dramas I watch
Yes, I love when there's romance in most of the dramas I watch too, but I hate when it's done childishly with a lot of gimmicky slapstick humour.
I love bad boy male leads.
But I hate when they bully other students or people
I love when one of my favourite kpop groups have a comeback
But I hate it when I realize that I will have to wait a longggggggg time for their next comeback.
I love it when my favorite kpop group/kdrama/kshow gets famous.
But I hate it if the kdrama I love gets prolonged because of how popular it is and the story line becomes all messed up. (sometimes it works but sometimes it really doesn't)

I love time travel stories.
I hate time travel stories with loads of plot holes.

I love detective stories
but I dislike when the atmosphere is too cold & dark
I like school dramas
i dislike the main female being dumb

i love manga turned jdramas
But I hate it when people complain that not everything is exactly the same

I love romantic comedy dramas
but I dislike that most of them get boring & stereotype after ep 8-10
I like travel in time dramas
but I dislike the drama "nine times time travel"

I like drama marathoning at rainy days