I despise Bongo Bongo and Morpha the most.
*SORT OF SPOILER*Bongo Bongo just plain scared the living daylights out of me the first time I played, plus each hand is like a boss within itself that you have to destroy. Morpha is annoying with the way that.. um.. he? She...? grabs you and flings you about. Plus, sometimes I would grab that annoying little bouncy thing with my Longshot, and it wouldn't quite make it onto the platform, so I couldn't slash it with my sword. Very irritating indeed.