I dislike it when a new character/ love interest is introduced in a romance comic, SOLELY to be the villain and create misunderstandings between the main characters. Why not at least make them likable, or act like a real person?
Oh god i agree with this.
I have been doing jujitsu for more than three years now and i still can't beat my master in a long way
Some really convoluted misunderstanding that “divides” the main cast that’s easily solvable by basic communication.
Also love triangles in any way, shape, and form
Asshole characters for the sake of being asshole characters or having asshole characters, with no explanation or necessity to their assholery.
Long as we're here.
When THE CHOSEN ONE has NOT demonstrated any reason to be 'the chosen one' and secondary characters have shown better potential to be doing the important stuff.
Like, why is the new character chosen to be the test pilot when there is already a 'best in the school' or Dojo or at the base or in the program or is already out there doing missions...?
Like, why are we going with this untapped potential over a fully skilled not-main-character?
The girl that gets a ball kicked/thrown in her face by her love interest. Every. Single. Ducking. Time. I JUST WANNA SEE A GIRL CATCH THAT BALL FOR ONCE instead of being carried of gallantly to the infirmary where he stays at her side asdfghjkl!!!
Oh, or: Oh no, someone jumps in fron of a car to save Love interest and either gets hit instead or both get away.
Major tableflip on my account in both cases.
Very spefically, gay person dying to act as character growth for the other gay character. Cheap revenge plotlines. Stop killing your gays, it's fucking awful and as a gay man growing up I literally could not see a happy future because representation MATTERS.
Very specific version of the people coming back from the dead: the fake out death. Like ok, I don't mind people coming back from the dead if that's a plot thing or if it's done well like certain ones where you have an obvious consequence because people aren't supposed to come back or you have a necromancer (on that note read the Necromancer manga if you can it's a fantastic example of sure people can come back but there are consequences and no one is happy in the end). Fine ok. But fake out deaths. You get 1 fake out death allowance from me and that's it. And that fake out had better have consequences. If you're constantly expecting me to grieve for a character like they're dead then bring them back next chapter, I'm going to stop caring. Or worse they're gone for a year or more to really trick you and then return but they return like it's nothing. Just like "oh hey I didn't die nvm" and the rest of the cast are like "oh hey good to have you back". It's like bringing someone back cheaply, but worse.
You know that trope where the fan-favorite character dies a horrible, gruesome death and comes back seasons later, not dead, body intact, same personality, with the same memories as before, thus making the previous death of said character hollow?
Also you know that trope where the least liked character for some reason keeps being brought back to life because... reasons?
coughs in the general direction of RWBY
(Yes I know it's not a comic but shh let me have my moment)
Okay so, something specific to Webtoons: Not a huge fan of the trope where the MC (usually female) is either average-looking or flat-out ugly, learns how to be beautiful/handsome, and a good part of the story is "will their peers find out their true appearance oh noo read to find out". It's the main reason why I never, and probably will never, read True Beauty. Read Lookism for a bit and stopped lmao.
(like, NOBODY looks that different when putting on makeup. You still have the same face. WHY does the MC in True Beauty look so different as opposed to having no makeup what-)
I heard Lookism IS good, it's just not my cup of tea, though.
Something I can add is the "over-hyped" antagonist. Like, every time he/she gets mentioned, everybody is losing their shit. And then when they clash with the protag, they get their ass handeled like they where nothing at all. This actually is mostly killing all the tension in a story for me.
I hate it when there's a team/group and it only has one female character. It's even worse if she's useless (other than maybe healing the guys when they get injured) and pines after the male protagonist.
She has no real personality and no character arc. Men get to develop and have epic battles where they lose, overcome and eventually win. Their relationships are fleshed out and full of drama, emotion and depth. They're the ones who are at odds with the story's antagonist and whose actions matter/ have consequences. The girl just tags along and acts as the team's cheerleader.
Monster tropes.
Just once, can I see something unique?
We've always got orks that are big humanoid pigs, goblins that are creepy little knife-ears, and slimes that are just little blobs.
Evolution is a thing, they should adapt to their natural environments. Show me a sea goblin, or a cave ork!
Perhaps the opposite of what many feel:
I'm tired of authors permakilling characters just for the sake of stakes. Oh, we have a new villain to hype up? Let me just take this very likable character and kill them off. Is it the final battle? Let's just murder half the cast, because that's necessary...
Even worse if the character is forgotten about after that, or if the survivors celebrate their victory after they lost half their group.
Nah, done with that. If you write a death, you better make it feel significant. I'd rather read a story where the characters have abundant plot armour, but when push comes to shove the losses feel real, than a story that just makes me want to distance myself emotionally.
I mostly agree with what's been said about bringing characters back from the dead or faking deaths. Though I think there's one kind of story than can get away with it, to an extent: time-travel story. Even so, it shouldn't come too easily... and it's easy to overuse it, just to show characters dying brutal deaths that don't actually have any consequences. (I mean, I do like several stories that do that. And I can see why writers would do that. But still. Overusing it makes it look like cheap torture porn.)
Unrelated to that, I don't think this was mentioned yet - I can't stand out extremely drawn-out romance. I'm all for a good slow burn, but if the story continuously relies on a number of contrivances (oh god, contrived misunderstandings are the worst thing) to keep the characters from getting together, to keep the "will they or won't they" for far longer than it can be fresh or engaging... then my patience may give out.
"Hey sis!" "Hey baby bro!" or any other clunky way of showing the audience two characters are related. There are so many possible workarounds it just sounds like the author has never asked someone with siblings how they talk to them.
Side characters that were once useful to the main plot(for a long period of time) and then become deadweight, or their personalities are forgotten, or they just become a joke.
pouring one out for you, Yamcha.
This might be a thing that some writers thoughtlessly copy from anime&manga, since in Japan, referring to your (particularly older) sibling with sister/brother is more common than using their name 
and it makes sense in a Japanese setting, I suppose, but otherwise, yeah it's kind of a lazy exposition thing.