Loads of things do.
Boring, whiny or annoying main characters, or their love interest is boring, whiny or annoying (in which case I *might* stick around just to see them get dumped).
Lazy exposition where something should have probably been properly written out, or anything that reads like a summary of events rather than a story.
Internal monologuing. I rarely ever find someone's thoughts or memories interesting.
Anything where the writer went for a really grabby 'hook' or starts in the midst of some hurried action and a page later everything slows to a semi-conscious crawl.
A major plot-turning point that hasn't even been hinted at earlier, especially if it's well into the story and revolves around a character who's only just been introduced, yet the relationship is important enough for the MC to risk everything to save him or her.
Writing so self-consciously beautiful it seems the writer is admiring themselves in a mirror. Or on the other hand, a vocabulary so limited it wouldn't send the average eight-year -old to a dictionary.
Predictable story with an outcome you can see by the second or third chapter.
One-too-many overdone tropes won't even get me to crack it open: some are, x villain killed MC's mum or dad and now they have to get revenge, anyone 'chosen' or 'destined' out of the millions of people out there but all they want to do is live an ordinary life, or must stop the apocalypse/end of the universe. Anything generic like vampire hunters, vampire academies or gangs, vampires or werewolves still in high school, any zombie apocalypse, ordinary MC crossed or got caught up in something involving gangsters or drug dealers, x race vs y race...
Villains with no decent motives, they're just 'evil' for some reason.
Stories that should have been political pamphlets or polemic essays instead.
Really graphic violence, especially if directed at children or animals.
Stories too fixated on the MC's shopping habits.
Domestics - stories that never leave the front yard. If I want to hear about squabbling in-laws I have five siblings I could call and in the era of Facebook I get my fill and then some of cute/quirky/weird/funny things any child ever does.