To be fair, every writer has this list.
The biggest struggle I had, and have seen other writers struggle with, is keeping the two worlds balanced. The main character Interference is Thalia Grace from the Percy Jackson and the Olympian series. By the time of the story, she's been immortal for a while now, and challenging her while keeping her as skilled as she should be was challenging.
Media, unfortunately, often dictates how certain groups of people are perceived in society. This is why representation is so important in TV, movies, and books. This need for representation goes beyond just race, gender, and sexuality. It is also important with personality types and niches of humans. For instance, the way awkward characters are treated is often a misrepresentation.
But everything has flaws in it, and Harry Potter is no exception. To me, the most annoying was her use of dialect, primarily with Hagrid.
So a while back I was looking for characters sheets and quizzes to help with the characters I was writing. Some were the typical character sheets - the ones made for authors. But I came across one that was for personal insight. Originally, I was going to tackle it the way I usually do. But a little ways into the first one I started having fun with it. I think I found out more about my characters through that.
A strong female character in fiction is often seen as a set personality - cold, vicious, doesn't take any BS type of girl. But why?
The number one problem with romance, as I said above, is when the chemistry seems forced. When two characters are forced together for no reason other than because they need to be in a relationship, it comes across as... well, forced. Force relationship are dry, and much worse than letting characters stay single.
And suddenly those character sheets go out the window.
There are certain ways fantasy has to be written. It's clear in every piece of it you pick up. But why can't authors break the rules? The answer is obvious - the Guardian of Fantasy.