What are some of your most hated opponents thrown at you in games? Because for me, I hate all and any oozes and slimes from almost any old school rpg. They always have annoying resistances, either to magic or to melee so you can never hit the darned things. And they also almost always come with nasty side effects to your party, like poison or confuse. A specific example is the corrosive oozes from Might and Magic 6. They resist melee damage, break you weapons, and poison. Ugh.

tinyE...

women!

I hate Regenerators, monsters in Resident Evil 4.

Mario is public enemy #1.

Any kind of boss or enemy that randomly disappears/reappears (warps).

But those were awesome. Besides, they just want to give you a hug. :D

Annoying pesky enemies that give little rewards.(Exp, gold, loot), but need to fight a mobs to these enemies to go anywhere. And will be worst if these enemies get stronger as you level up, tarnishing the feeling of empowerment when you level up. (FF8 flies & man eating plant & caterpillar......)

Hence I enjoy summoner type char where its main job is just collecting loot where his minions do the hard work.

Probably crows in RE games.

Goombas...AKA Kuribo... I mean, it's a mushroom! How can they defeat Mario and make him fall off the screen if he doesn't jump on their heads correctly? Instead, they should just fall apart as he walks past them! =P

Because he don't charm them with a star?

In a bad way :

Nemesis. RE make good zombie games, but RE3 is just one perpetual tedious boss fight, got tired of it pretty fast.

Trigens. They defeat the very point of Far Cry.

What was the name of these shrieking giant bird things, that you were enountering every three steps in Morrowind ? Annoying as hell.

Homing exploding kamikazes enemies in general, especially the biological sort.

In a good way :

Facehuggers. Heck the very sound of them in AvP makes me run away.

Cyborg midwives. The Many. Shodan. Arggh, everything in that.

Whatever is that thing in Homeworld Cataclysm.

Phil trouble he is double he's an eye that's no lie.

But that's what made it so scary, it basically broke the "rule" the previous RE games had which is that once you go through a door the monsters can't follow. In Nemesis even if you ran away from Nemy through a door, you can be sure in a few moments you would hear "STARS!" and he would keep following you.

Dragons.

Myself.
Err... I mean, when a game tosses in someone who can do exactly what your character can, has the same gear as your character does and is overall your character's doppelganger. Bonus hatred points if (s)he mirrors your character's moves.