It seems to rotate on a daily basis with the fish. Most recently we hated our male spotbreast angel after he snapped and and started beating his girlfriend nearly to death. They'd been together for 18 months without a problem, then one day it's like he blew a gasket. She got a restraining order against him and lives in our shallow reef.
Our purple tang, aka; Queen *****Toria...is frequently on the Dislike List only because she's the boss and hates everyone else in the tank. Thankfully she doesn't hate us...yet.
The female Spotcinctus clown is on the hate list after killing her boyfriend last week. He was WAY cuter than she is.
Our yellow wrasse, because picking him up off the tile floor is getting old very quickly. 8 times, as of last week. And we have a secure lid! I swear he waits for it to come off and then...Geronimoooooooooooo!
(Incidentally, our sixline wrasse is a perfect gentleman, but I think it's because the yellow wrasse is twice his size and keeps him in check.)
But the critter that is always on Today's List of Hated Inhabitants is the skunk cleaner shrimp. Feeding the bubble tip anemones, elegance coral or trachyphyllia goes like this: 1) Turn off flow. 2) Place food on critter to be fed. 3) Immediately grab long stick of rigid airline tubing. 4) Spend the next twenty minutes whacking the shrimp as it tries to steal the food, even if it is deep in the mouth of the anemones or coral. If she was delicate in her food extraction, like a surgeon, it wouldn't concern me so much...unfortunately she's more like a rabid butcher with a bad case of tremors and a cleaver in each hand...err, claw.