The ole “using descriptive words that fit the plotline’s theme” tactic...
Metaphors can be dangerous at the best of times.
As long as I'm here, more Mary Sue tropes that bother me:
Being awe-inspiringly attractive but either A) not knowing or B) having unrealistically low self esteem
everyone loves, or hates, your character with no good reason. BONUS if your MC is a girl and other girls are mean to her just because they're jealous
The anti-sue. Everything a regular Mary Sue is BUT they have attitude, are mean to everyone, and are fond of fishnets.
On this topic of the MC hating everyone, they'll be mean but people won't seem to mind. In fact, they'll readily forgive them, and there are no real consequences to MC's actions
Mary Sue has no flaws, but author insists MC is "clumsy" as if that constitutes as a genuine character flaw
Over-description of every scrap of clothing ever that ever touches Mary Sue ever (i.e. my tattered, limited-edition blood red converse worked wonderfully with my cotoure black skinny jeans with rips at the knees, and also complimented the Three Doors Down band t-shirt with cap sleeves and a v-shaped neckline. On my hands were a pair of fishnet, fingerless gloves ripped strategically to make them look super cool, and I had a red-and-black flannel shirt tied around my slim waist in two perfect sailor knots.)
STOP THAT'S TOO MUCH STOP PLEASE
NAMES LIKE EBONY D'ARKNESS DEMENTIA RAVEN WAY
Mary Sue has a horribly tragic past but is cheerful and unrealistically undamaged despite it
Mary Sue is any kind of magical creature hybrid of more than two (I'm personally cool with two because Vampire Diaries proved this could be done in a tasteful, interesting way. But if Mary Sue is a vampire-mermaid-werewolf, she starts to look silly.)
Okay I could go on and on, but I'm just gonna drop this link for a Mary Sue test instead XD
Oh my god that's a combo. A 'group makes noise and gets caught' situation can be great and even funny if they're somewhere safe or unaware they're being followed, but having them suddenly forget what they were doing to talk Because Plot is unbearable.
Two characters in a love triangle randomly fighting over the third in general is also rarely done well and sometimes feel outright gross. I might be sick of it because my country is way into soap opera and it's always on TV somewhere, but the third person should not be turned into a trophy or just stare at two characters they supposedly love acting childish(unless it's part of their character that they have a very short fuse, but sometimes it's hard to believe). I actually really like the ending of Super Mario Odyssey for subverting the cliche, even though the plot is a footnote there.
Just finished Code Geass and I have another thing that INFURIATES Me. When a character can solve so many of their problems just by telling the truth but they abhorrently refuse to open up to others and it ends up ruining everything. It twists my stomach to the point where I don't wanna keep watching, reading, anything.
This one is probably one of the most frustrating things, especially when the character has like... absolutely no reason to keep it to themselves. They just do. And cause everyone problems.
I read a lot of romances and more likely than not, this kind of keeping important things to yourself and causing tons of unnecessary misunderstandings will make me put down a story unless there's a really good reason for it.
It makes me so incoherently frustrated that I can't enjoy the rest of the story. My entire mind is focused on how that scene would change if the secret was known or how the characters would react
They only ever trip dramatically into the arms of their lovers. I wouldn't even describe myself as clumsy, but I trip, drop, and bump things WAY more than characters who are actively described as clumsy. 
This is wildly off topic from the most recent comments, but sometimes I struggle with the maid and/or butler plotlines. Especially when they’re going to end up being the romantic interest. The “Master” thing doesn’t do it for me, or the maids/butlers fighting over who pleases the master more. The one that’s favored usually gets ostracized and the master is almost always an asshole at the start.
Maybe it’s because I’ve seen too many of these plots?
(Though, I did love Kuroshitsuji)
OH another thing is I become very wary of BL's where one of the main couple has a traditionally feminine name (and I CHECK with behindthename2 as sometimes names flip-flop genders over the course of history).
I just find that a lot of the time in these cases, the 'uke' is usually just a waifish female insert and it's not a trans/non-binary situation.
I need to keep in mind to check there more often if I do romance stories in the future with normal names. I only go there sometimes to make sure it's the actual spelling, or to choose someone's name when I'm out of ideas. I didn't even notice the gender icon a few times...
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. -_-