Got a bunch of dramas I want to see. I prefer k-drama with about 18-20 episodes. 

1. Romance where the male lead is an infinite onion and keeps suprising the viewer with new talents, knowledge, history, secrets, etc throughout the whole series.

2. Cute innocent drama with no angst and no bothersome love triangles or misunderstandings which hurt them.

3. Intelligent, strong male lead with amnesia.

4. Male lead who does something amazing for the girl he likes and hints of what he's doing is shown in each episode until the big reveal that blows everyone away. I guess I'm going for a bit of shawshank redemptionenesque, but romancewise.

If you can think of anything that fits, big thanks :)

Falling for Innocence (4), Good Doctor (1), Kill Me, Heal Me (3?,4), That Fool (2) - they're somewhat different from what you described here, but they're really good dramas and I think you'll enjoy them anyway.
Sounds exactly like I Remember You
Ask and you shall receive.  The must see drama for you would be hands down.
You who came from the stars