Here they are:
Tdrama
Drunken to Love You - Romantic and funny

Kdrama
The Greatest Love - Must see
Robber - One my favourite drama ever!! So underrated :'(
Couple or Trouble - An excellent romcom based on a USmovie
Witch Yoo Hee - Cute dramas with the pretty Han Ga In

Jdrama
My Boss My Hero - A 27 year-old yakuza boss has to go back to high school. Funny
Mendol - I liked the craziness
Sailor Fuku to Kikanju - A shy high school girl has to become the kumicho of a gang she wasn't even aware of. (-16)

Anyway I liked these dramas and want people to have the opportunity to watch them :)
Kingyo Club H2 RESCUE Not underrated but still not on your list: 1 Litre of Tears Runaway ~ Aisuru Kimi no Tame ni ~ Rich Man Poor Woman Rookies Orthros no Inu