I hate those bloody Piranha fish things in Ninja Gaiden Sigma, you attack one of them and the whole pack attatch themselves to you sucking your blood. The mutants in Rage got on my nerves too, they would dart about the screen and had me wishing i had Wii pointer controls instead of dual analogue so i could pick them off easier.

Haha, I actually didn't think the red dragon was that bad.  Now the blue dragon gave me some trouble.

Ghirahim...enough said. Constantly grabbing your sword all the time, it's so damn frustrating.

and EVERYTHING in Demon Souls

The End

Nice one Xxain. Metropolis Zone was a heck of a challenge, and they mocked us further by giving it 3 acts. I remember I was so happy once I beat Act 2... only to hear the theme come up (although the Metropolis Zone theme is amazing...) again! Curses!

Those exploding Starfish were evil as well.

Didn´t  see that comming. But come on "The End" was not annoying he was rather frustrating.

Pretty much every single monster in edit: I don't exactly remember the name of the place, but it is the last tower(dungeon) in the game in FFIV.

I would say the Cliff Racers from Morrowind, even though I kind of like them. Every time you hear them and decide to fight you can be sure you have to wait at least a minute until you can finally reach them... and there are so many!

Legendary difficulties.

Enemy Elites. Even Noble Six cant defeat these guys one to one.