Oh definitely mischaracterization and the possibility that my characters will get shipped uncanonically. Like, I have such an "on the fence" view of shipping. Part of me is like, let people ship what they want! And then the other part is afraid as a creator, because I wrote my couples as they are for a reason and the idea of someone just going "nah" feels disrespectful in a way.
I also agree with the idea of someone creating fanart and making money off the characters I have spent so much time and energy creating. That would wreck me. My characters are all pieces of me, so someone taking pieces of me and selling it, doing what they want with it and ignoring my wishes as a creator scare me.