Keoul said:
-Constantly needing to change tactics (Mr freeze in Arkham City)
I actually really like it when boss fights do something like that, it keeps it from being repetitive, especially if it's a boss that keeps destroying you so you have to start over from the beginning. Well, when it's done well and telegraphed clearly that you'll need to do something else, at least...
OT: One-Hit Kill attacks. Good lord those are annoying.
And I don't particularly like when bosses spawn smaller enemies, it smacks of lazy design to me, like they couldn't be bothered to make actual unique bosses so they just super-charge a normal enemy, maybe give him an extra attack or two, and then have him summon the normal mooks you've been charging through every 25%. Boring.
Stun/knockback attacks are hell too, especially if your character is particularly slow getting back to their feet.
But what will piss me off more than anything is a long boss-fight that doesn't have a mid-boss checkpoint. What's that? You spent the last fifteen minutes whittling away this guy's health, only to miss a dodge and get smashed into pulp? Haha! Do it all over again!
Demon's Souls makes me rage a lot...