For me it's harem or female characters in general who were obviously just there to be eye candy. Like they don't act like real women at all. It irritates when I reading a book or watching a show where a bunch of women are fighting for an absolute loser of an MC ?
Oh and also the indecisive mc, who all the girls like because he's "nice" but really he's just indecisive and a pushover.
Also, tsunderes. They many of them are just physically or emotionally abusive then labeled as "tsundere."
Then there is the MC who wants to be low-key to stay out of trouble, but then constantly not explaining themselves or keeping certain information about themselves because it's too "troublesome" to explain, while the misunderstanding is actually causing more trouble than if they had just explained themselves. It drives me nuts, like are you sure that's less troublesome???
Lastly the overly arrogant brute MC who chooses to solve things in the most brute way possible and later cause several problems to happen later due to it. Like he defeats one enemy, because he did it in the stupidest, most brute way possible he creates like 5 more enemies ? like bro stop. Just think things through for a few seconds for once. You don't have to make a show of your power every time you kill an enemy.