Off the top of my head, Gastropods that snipe you during the Empress fight and any enemy that inflicts a movement-hindering debuff for more than 20 seconds
Terraria Community Forums
J Bame
Kane Schmitz
Back in 1.2, I hated the Gastropods. Weirdly, I don’t find bats that annoying. The worst thing would be Giant Shellies. Along with Lava Silmes in Expert/Master Mode.
SaltyDog
Anything in the jungle, the hallow, the underworld, the dungeon, the corruption, the lihzahrd temple, the mushroom land, marble caves, or when fighting the celestial pillars is annoying.
SaltyDog
Oh, and all events. The only part of the world that's okay is the forest, although, though they deal hardly any damage, the slimes are constantly dealing damage when they attack you because they just sit on you and that can get to be quite annoying.
Jackiethederg
Cave bats and hornets.
A (Pioneer) Rock
for me it was red devils and arch demons
Digitus
Guide.
SaltyDog
To be honest, the guide is actually kind of annoying.
appleNsauce
Harpy
SaltyDog
Wait, sky island enemies are annoying as well I forgot.
Mushy Chlorophyte
Master smol bee.
Evil Ghost Lady
Clingers.