My biggest gripe of comically incompetent characters has already been well addressed elsewhere, so I'll go with my second least favorite trope: every single character being unlikable to the point where I have no investment in them.

There's this running undercurrent of horror films involving the worst people getting their comeuppance (which I'm cool with), but if every character in your movie is a serial abusive partner or a hyperaggressive asshole or the least charitable alpha cheerleader archetype or whatever I'm not going to feel any reason to care when they start getting offed by a ghost. It can be cathartic if there's one or two characters that fill this role, but if I can't make any connection with any of your characters then the film is just boring and painful to sit through.

Between these two tropes, there's not a lot of horror I actually do like.

Edit: One other thing that's not entirely on-topic, but relevant both to my general distaste for horror and the fact that someone mentioned Nope elsewhere: I think horror falls apart for me because it mostly only works if all your characters are useless. Nope is a fantastic film to me because the main characters are all competent, smart people who leverage their skills and strengths to overcome something much bigger and scarier than them, and outside of outright supernatural immortal slasher villains there's not a lot of horror antagonists that can't be felled that way, but it rarely happens. Nope is two hours of metaphorically watching neolithic humans take down a wooly mammoth because they bothered to use their brains, and it's awesome.