When it feels like the author is just spewing the entire dictionary at you and they don't even know what half the words they are using even mean...
Reading works like that is especially tiring for people with first language other than English. Whenever someone puts lots of sophisticated words in writing, I just can't focus on reading because I need to check the meaning every now and then or focus way too much on how should I actually read that word.
I hate this so much.
My English is not the best but it's not HORRIBLE, but with novels like this I keep having to look words up in the dictionary, only to have the word have little to nothing to do with what the author was trying to say and confuse me even more.
I remember when I first started writing papers for my English BA, I was googling so many synonyms to words in attempt to make my paper sound more intelligent. It had the opposite affect. My professor basically came up to me and was like “cut the shit and write as if you’re talking normally.”
I owe her a cake.
When writers want to put drama in the story but don't want to try to use that drama to showcase a character's flaws or create real consequences so they go for the cheap misunderstanding trope where everything could have gone fine if someone had just had basic communication and just wastes time in the story because you know it's going be resolved anyway. And of course the misunderstanding clears up and everyone's happy in the end anyways. -_-
Yeah, it's just annoying because it feels like the writer doesn't have the guts to make their characters do something disagreeable but at the same time still wants a conflict in the story where characters get mad at each other..
Anytime a character is purposefully eavesdropping on their lover, but don't have the COMMON SENSE to finish the job and run off upset, I get irritated. Like, you went out of your way to listen in on them -- FINISH listening.
And then they wanna get mad at their lover instead of TALKING, and now their lover has NO IDEA why they're pissed. Come to find out, it was all a misunderstanding, and readers are supposed to gloss over the fact that this character 1) didn't respect their lover's privacy and 2) made a snap judgement against them.
Also, whenever I read a novel that has the hero/heroine be "this nice person who never gets love because they're SO different but SO misunderstood", I cringe. They're always brunette (because obviously blonde people are so arrogant and popular) and they always wear glasses (because you can't be attractive with glasses). They also make snap judgements towards other people, and the reader is supposed to agree because the other people are so paper-thin shallow and underdeveloped.
I hate it when an author's sole purpose for writing a book is to show off all their "cool" "obscure" knowledge about a certain decade they they want to impress is waaaay more awesome than anything else.
References and call backs are fine, but when the references engulf the entirety of book, and detracts from (or omits) any character development, plot, or atmosphere...well, then you've lost me.
Ridiculously possessive male love interest who are supposed to be cool according to the author. I just don't get it at all about what so interesting about them; they are always good-looking and have a nice body, but their personality is often zero but their obsession to their love interest.
Such kind of story also can come across for glorifying abuse and in-relationship rape, because that's how the guy always act (controlling, demanding sex, etc.). The author often justify it by saying it's their right being the "Man" in relationship, or for protecting the love interest.
I once read a werewolf fiction on Wattpad (a popular one, but what do I expect). It's always an alpha male looking for a female mate (usually called queen or luna), and the rival is always some rogue packless wolf.
Do you know what the romantic first words the alpha said to his luna? "Mate! Mate! Mate!" and "Mine!" 
He also spent most of their interaction
by kabedon-ing the girl, trying to kiss or grope her, and fighting any guy who approached her by grabbing her close and growled "Mine" angrily to that guy.
So hot 
Another thing from the same book I was talking about above (about the MC and the love interest arguing about which one the mc should end up with, scroll up):
So one of the LIs is actually a long-lost prince of the MC's kingdom/country and has been imprisoned secretly with his mom, the queen. So the queen and the MC's mom were close friends back when they were kids, and the queen goes like "yea, your mother and I planned for you and my son to be betrothed, but obviously that didn't happen!" and the prince LI hears this
and looks at her like he's in love with her?????? What??????? I wouldn't hear this news from my mom that I was supposed to be married to some girl I hadn't seen in 8+ years and barely remember and think "ah yes. she must be the one."
then the prince insists on going with the MC and her other LI, to which his mom says no (understandable he's the only fucking child of the monarch and doesn't know how to use a gun oh fucking course sneaking into a highly guarded government facility is a bad idea) which leads the other LI to be killed and MC goes into grief.
Like she's in her room, not eating, not talking to anyone, and this prince, has the FUCKING GALL, to slip into her room and say "hey MC will you marry me? you can be the queen" LIKE BITCH WHAT THE FUCK?????
Even more shitty: SHE SAYS YES BUT ONLY BECAUSE SHE BELIEVES THIS SHITTY PRINCE WILL HELP HER MOVE ON.
MC YOU ARE 14 YEARS OLD. YOUR CRUSH ON YOUR VERY BORING LI IS AT BEST A PUPPY LOVE, ESPECIALLY SINCE HE'S LIKE 17.
It's been over a year and I still don't know if I'm supposed to like or dislike Shittier Maxon Schreave, but my strong hate for his character and how terribly he was written still continues.
(added bonus: this book spawned two more sequels. I'm not reading either of them and I never will.)
Anyway I should seriously consider a career in online book reviews. Typing these out is fun.
When the first paragraph (or couple first paragraphs) is basically MC describing their looks in a long and convoluted way. Then I know I'm in for a ride. Also, the eye colour cannot be something normal like blue or brown, naah, it has to be of the colour of the storming seas on a windy day or something like that.
When the MC is a girl that hates on other girls and bashes using makeup. It's really shitty attitude and I honestly hate it. I stopped reading book when MC was being mean to other girls because they are all 'sluts' and 'bimbos'. I honestly don't understand why the author thought it would be a good idea, unless you want your character to be completely unlikable.
I also have the 2nd Lead Syndrome. I don't understand why, when there is a love triangle the MC always chooses the abusive guy instead of cool and kind guy? And if she chooses the abusive douche and there is still a book or two, why can't the good guy get someone that deserves him instead of still trying to get with MC? Ughh, and killing him to get rid of the problem is even worse.
I remember LONG AGO reading an adaptation of My Immortal on Smackjeeves that was suddenly cancelled because the author found out they lived in the same neighborhood as the supposed author and didn't want to out them. If it was true or not(or if the person only claimed to have written My Immortal for attention) I have no idea, but according to the comic artist, the person was completely clueless to the memes and criticisms, and just thought their fanfic was revered worldwide.
It's definately one of the biggest mysteries of the internet. Too early to be interviewed, too late to be approached years later when they went to see what happened to their little Harry Potter story. I'm more of a fan of the very short legendary Doom fanfic, but iirc that one has more evidence to being just a parody.