I've wanted to do this topic for a while.
Just post what mosnters and themes you dislike and like most.
Here's mine:
Monsters - like: jellies, chroma series, undeads (except the ghosts)
dislike: DEVILITES ASDFKDSJGSKDDFG (sorry but they're just terrible), alpha wolvers (when there are lots it's almost impossible to kill them all in a good time without getting hurt) lumbers (SO. MUCH DAMAGE. ;; ) and those robots with lasers. lol
Themes - like: jelly, poison, undead.
dislike: DEVILITES. SHOCK. ;; and fire too. and beast sometimes. the rest is ok actually
Well, I think devilites are a given HATE.
Jerks.
Likes: Jellies, Lichens, Zombies, Chromalisks, Thwack hammer / FT gremlins, Gun puppies, Lumbers,
Dislikes: Devilites (they're always throwing something. It's like non-stop aggro from a distance), Alpha wolvers (If your'e close when they start their attacks, your shield is gone. GONE I SAY), Silkwings, T3 menders (Menders in every tier except tier 3 aren't even important, but T3 menders? FFFFFFFF I can't even begin), Bombing gremlins (they're fast with the bombs and faster on their feet. the only time I can hit one is if I walk into a bomb myself), Cyclops constructs (the ones that shoot lasers that explode, It's too powerful IMO).
In all honesty though, you play long enough you begin to resent everything. EVERYTHING.