Before I learned to drop a drama (not to put myself through torture), I can't believe I finished watching over a dozen bad dramas. Also at that time, there was no MDL to help me weed out bad dramas, so now I don't watch dramas below a certain rating. So here's my pick of the worst:
From the ones I completed:
Bad Couple; Brown Sugar Macchiato; Triple; Bad Romance; Couple or Trouble
From the ones I dropped:
A Love To Kill; Beethoven Virus; Black & White; Boys on the Run; Cinderella's Sister; Hana Kimi (Taiwan); History: My Heto; Rainbow Sweetheart; Snow in August; The Queen Returns; Tokyo Juliet