I hate when the bad guy is able to easily sow mistrust between characters who are supposed to be lifelong friends. You know, making accusations without any evidence and then the heroes start to doubt each other. It's like don't you see that the bad guy has a reason to make you believe them and wants you to fail in your goal? They have every reason to lie and if anything, you should just talk it out.

Another is when the bad guy joins the party and still does a lot of their evil things like killing but it's okay now because they're on the good side now. Kinda takes away from the reality that certain actions are bad regardless of what side you're on.

I can't stand young-looking old or ancient characters who are just an excuse to make them look cool or worse, used as an excuse to sexualize someone who looks like a child. It's such a wasted trope sometimes. An ancient person could have stories about their experience of the world or contribute with their insight in some other way. I think Umbrella Academy has a lot of flaws but I thought 5 was a cool exploration of a character like that.