Which Firefly character do you find hardest to write? I find myself struggling with River. Especially in post-BDM fic because I want to show that some progress has been made in terms of her mental health, but I don't think it's appropriate to show her as being fully healed either. And in pre-BDM fic, I find it sometimes hard to capture the 'she's-crazy-but-she-kinda-makes-sense' vibe that the show's writers did so well.
I honestly don't find any of them hard to write. Some are harder for me to think of good stories for, but I enjoy working with all of them. The only main character who hasn't gotten much play in my fanfic is Book. I think I've maybe given him a line or two, total. Whoops.