That would have to be "Misty". I adored the first 3 episodes, and liked each episode after these 3 a little less until, by the end, I hated the show, the show's writers, the shows characters, the show's costumes, the plot, and the actors. I've watched a hundred kdramas and cdramas, and dozens and dozens of them have been disappointing, but only "Misty" has the distinction of being hated.