The one fish I would say that I genuinely HATE are freaking blood parrots. Absolutely useless hybrid mutated deformed monstrosities and I have NO CLUE why anyone likes these things.
Really not a fan of piranha or oscars either. I wouldn't say I hate them, but zero appeal factor for me. Ugly fish that don't live up to the hype around them.
Most tetras. Never really kept them much in 30+ years, obviously because there's not much interest for me...but recently actually went digging through tetra species trying to find something to keep a school of for some upper/mid level activity in my largest tank. Quickly discovered that there's maybe 4 or 5 species I'd ever vaguely consider keeping, most I just find ugly as hell.