My single greatest peeve every time I see it is a simple one, but complex at the end of it.
Romantization.
Particularly I hate it when the story makes a terrible situation into a positive thing by the means of showing it's better than it actually is, and telling you 'don't think too much about it'. There are thousands of examples I could give here, but I'll focus on four in specific.
1 - Romantization of Violence - Do not get me wrong, VIOLENCE CAN BE FUN, but there is a big difference between a story that puts those elements as their core, and one the taps into that pool just for shock value, and it becomes blatantly obvious... When the 'seemingly good' character goes on a passion fueled killing spree you can usually tell it was done as sort of a tribute to violence itself and not as a meaningful development.
The characters need to experience violence as a more realistic thing... Sure, some people don't break down and cry when they make someone bleed or even kill, but what any sane person will tell you is that violence has internal consequences for you as well as the person who you hurt. The leap from 'I want to help people' to 'i'm okay with killing people for the people I care about' is HUGE and should not be downplayed.
Expressing that is key to not romanticize violence... Especially when a story dabs a lot into the moral grey area of 'hurting people for the right reasons', that violence has to be well explored... either that or the story needs to be set up for it to fit like the horribly deranged and desentized world of Dorohedoro, no one bats an eye for violence there because it is absolutely everwhere and its a horribly gruesome but fun spectacle.
2 - Romantization of Envy - The big breaking point for me and most love stories out there... Envy is usually never done correctly in any story, with very rare exceptions.
There is certainly value in envy, like any feeling it doesn't come from nowhere... A personal insecurity, abandonment issues, overbearing family, all can be the source of envy in one way or another, but it few are the stories that care to explore that.
A lot of times envy is portrayed as the best emotion to display when in love, to the point some people actually say 'its not true love without it' like... How arrogant is that view? If you don't objectify the ownership of your partner you are probably not in love with them? WTF is that logic?
Sure envy is a natural biological reaction to some people, but not all, and even then a runny nose is also a natural biological reaction and you don't see people proudly presenting theirs as a good character trait or something positive do you?
Working on that envy, learning to trust and moving past those hurdles can be amazing development, but more often than not it gets 'side-resolved'
Like the person causing the envy was 100% trying to steal the partner and they get rejected making the whole thing justified... Or the partner apologizes and somehow is forgiven for a crime they never comited in the first place... And the story moves on like nothing happened because the writer was too lazy to think up a better plot.
Don't romanticize jealousy people... its annoying at best, toxic and destructive at its worst and it most definetly is NOT a quality.
Don't believe decades of media telling you otherwise.
3 - Romatization of trauma and medical conditions - Don't... Simply don't...
Like i'm not a better person because I suffer from anxiety and criplling depression, it doesn't make me stronger or braver to go about my days suffering... And I don't want people telling me otherwise or pitying me for it.
It is ok to display those conditions and trauma, and it is perfectly fine for the characters to break down, cry and curse at the wind, just never make it seem like they somehow grew a superpower BeCAUSE of it... They grew a super power IN SPITE of it.
Bruce wayne is not better because his parents died
Toph is not better because she is blind.
Edward Elric is not a better fighter because he lost his arm and his leg.
People are not better because they have a condition!
So many times have I seen this horrible trope where like a character loses a limb and gains a superpower in return, or they are seen as highly senstive because they are blind and became bat like... It is perfectly fine for those things to arise, but never make it seem like that terrible condition somehow made them 'better' than someone else.
Disabilities should be treated as disabilities... It is perfectly fine to showcase that the character has an admirable will and personal strenght for moving past their disability, its a whole othey thing to say being crippled is awesome because you get superpowers.
4 - Romatization of poverty - It is a horrible trend i've seen lately to romaticize poverty and shitty life conditions... Like somehow it is better to live a dirt covered life in an area with no basic sanitation because there are birds are flying around, or because you have really nice neighboors who are a comunity and appreciate you.
It is important to say the whole 'money is not everything' but we in the real world know money would solve a significant chunk of our reasons to worry... And it's not like everyone gets 'corrupted' by money, it is not a magic demon like the greeks believed.
I sure as hell would love to provide a good life for my family and my partner has a mother who is suffering from some life long conditions and having money would mean he could spend more time with her as well as take better care of her... And I am sure anyone reading this can think of at least a few problems that would disapear from their lives if they had sufficient money.
Like the above point... poverty is a condition, it is not to be celebrated and not to be made into a happy musical number.
5 - Romantization of duty - Hate this one with a burning passion... The whole 'die for your country/clan/group' thing, it is not so much bad as it is naive for me.
You care for the people you care about, but at some point someone might try and bundle those people into groups to make you think they are your loved ones too... That is disigenous and manipulative, and characters not seeing that makes me roll my eyes.
If the character is the type that would fall for that, i'd believe it, i'm not happy with it, but i'd believe it... Call my cynical if you may, and this is the least relatable point I am making here, but I just don't buy it.
Duty is a complicated thing, but a characters loyalty should be made clear, and why they believe anything is the best path should be explored... A character that just goes ahead on a suicide mission because their 'lord/commander/ruler/authority figure' said so is not relatable to me at all... And most definetly should not be put at the helm of a story.
At some point that loyalty has to be tested, that faith in the system, that resolve... Otherwise it feels shallow and pointless.
Anyway, I already have a big enough wall of text, so I think that's enough to make my point
TL:DR - Don't romanticize bad shit.