Hate is a bit too strong but there are some drama I didn't like:
Boys Over Flowers and it was one of my first dramas so I guess it just didn't suit my taste.
Marriage not Dating, when I think of it, this drama was a total letdown and the synopsis completely misleaded me, I expected something different,
Koe Koi, I really didn't like this one, it was so boring and dull and I didn't like the characters.
KILL ME, HEAL ME : Maybe I can say I hated this one (well not really ahah), it was illogical, boring, and I disliked so much the female lead and most of the cast anyway except Ji Sung and his secretary.
Moon Lovers: Scarlet Heart, I don't have words to express how frustrated I felt while watching this drama, I completed it only for Lee Jun Ki.
Surplus Princess, I simply found it stupid and pointless.