Most Annoying Video Game Bosses / Levels

[Yugi]

Death from Castlevania Aria of Sorrow.

Elesa and her fucking emolga

Magic Master from FFVI.

[tfender7]

Water Temple. Ocarina of Time.

[Yugi]

I can't believe I haven't mentioned this boss yet.

DEMYX

He has annoying attacks that can knock you into the air, flunkies that can gangbang you and leave you helpless, a reaction command that does a crapload of damage EVEN IF YOU START WITH DEFENSIVE PRIORITIES, jump's around the stage, leave's very few openings and has the second highest HP total of all the ORG.  13 members.

But Here's the kicker.

At any point in the battle (he uses it at the start of the battle), he can shout "DANCE WATER DANCE" and he summons 10 water clones, which, if not defeated in 10 seconds, will end the battle with no explanation as to why. Also, he loves to SPAM THE HELL OUT OF THIS MOVE, EVEN ON BEGINNER DIFICULTY.