I like that a big part of the Sambucky relationship is often just Sam giving Bucky full permission to be a little fucked up. Not in the sense that he recognizes his mental problems, but also because he sometimes just shrugs and allows Bucky's worst instincts to take over. (Which is mostly a fandom thing, but a small part of canon too, since Sam went with Bucky's plan to free Zemo with very little push-back, for example..)
It gave me the idea for a story where after Hydra everyone around Bucky wants him to move on from his traumas and heal, but Sam gives him the space to also be furious and unhinged about that. Like... all the other people would say: "what they did to you was awful, but the best revenge is to live a happy life <3". And Sam's like... "no, the best revenge is to wake them up with a gun to the temple in the middle of the night and to burn down their home, actually. here's a lighter, are you free this weekend, handsome?".
I don't mean to say that other people don't understand Bucky's anger, but they believe it'd be healthier for him to deal with the pain only by finding hobbies, adopting a pet, eating nice food etc. Whereas Sam offers all those things with an extra dose of pure vengeance. One night he takes Bucky out to a nice restaurant. The next night he stands aside as Bucky beats the shit out of some doctor, who experimented on him in 1989 and then helps him cover it up.
This dynamic would probably work better in a AU with no powers where they're regular people and where Bucky's been kidnapped or integrated into a cult that ruined his life. But it could apply to the canon too, in some ways.
I just like the the idea of all the well-meaning people in Bucky life trying to put as big of a distance between him and his abusers as possible... While Sam - who everyone sees as a rational almost-pacifist with a lot of empathy - helps his boyfriend hunt these abusers for sport.
Asian Tim/Hispanic Jason from white people (Blasian Tim not included)
"Tim killed hundreds of people"
Cullen being one of Bruce's kids (have they literally ever had a private conversation. Have they met.)
Bruce being a business idiot and Lucius basically running WE for him
Cass being completely mute
Tim hating Dick and never forgiving him for the Robin thing
Damian never repenting, changing his personality and morals, and becoming close enough to Tim to proudly admit he's his brother
Dick not having any relationship to Kara Danvers (THEY. ARE. FRIENDS. WITH. ROMANTIC. TENSION.)
Babs being Cass's mom (I've talked at length about the sexist undertones here). Sisterly relationships are not "less important" than motherly relationships, and unless I'm missing something, I've never been able to find a single instance of Cass calling Babs her mom
BatJokes, Bru/Harvey, BatMask (specifically when the author has it canon in their AU that one of them seriously hurt his kids like in canon)
SlaDick. I just...don't like it. I really don't.
Jason and Tim never making amends (honestly don't know why everyone wants Tim to hate his siblings lol)
Duke innocent uwu boy
LADY SHIVA NOT FUCKING EXISTING
Edit: I was wrong about Cass not calling Babs mom, and someone corrected that. Thank you for correcting me, and I apologize for putting that on this list.
I still hate it very much, but its canon. So it shouldn't be on this list.
Also: these are personal opinions. I am not the arbiter of fanfiction. Write whatever you want forever I do not care. These are things I dislike. Don't take it personally.