Sex scenes. Definitely. I much prefer some insinuation, innuendo if need be...I can imagine quite well the how and what...it's almost exclusively second grade vanilla anyway.
Poor grammar - at least when it's much worse than my own as non native speaker. A distinct pet peeve are the, oh so frequently appearing, homophones. - I only have a 30 inch waste, because I waist so much of my time in the gym. 😉
Long winded description of eye and hair color, body shape and what not, of every, even minor characters. It's never necessary for any story...readers will always picture your characters in their mind differently.
What makes me actually quit a story?
Repetitive plots by the same author. When I realise, I have read it all before - and there is absolutely NO new twist, character development or a new/exciting finish...
Or, when I get the feeling an author has run out of ideas, and either rushes the story to a poorly planned out and unsatisfactory finish, or some weird "deus ex machina" plots get introduced, in an - usually futile - attempt to save a storyline that got stuck in the mud, or run up to a dead end in a single track street.
Preaching. I stopped following an author when after his first story, the second and third promised to be just more of (in that case) a pro-catholic proselyticing. Mind you, characters can have their faith, cherish it, be destroyed by it, but I don't want sweetly sermons constantly in the storyline.
Pet peeves? Too obvious stereotypes. Overused plots - one more accident killing both parents at once, and I start screaming!
Trigger warnings. Absolutely. Spare me those, as long as the bible is a topic in school still. I can deal with emotions, should they overcome me. In fact, I consider writing to be good when it can actually change my mood - either direction.
I am sure I can find more....but you get the idea! Besides, I rather see what you guys have written for my perusal and enjoyment now, than spend too much time thinking about the lttle things I found annoying in the past! Keep up your work, and have my sincerest thanks!