Feet in general due to lack of practice. But for males, I can't draw their legs x.x
I'm used to drawing curves since most of my subjects are female. Removing them always looks weird to me and I end up too frustrated to want to continue.
My solution? I'm making myself a male OC so I'll end up making art for him. Using references while drawing helps actually. If I can make myself practice it more I'll probably get better.
Unfortunately I don't have enough time to do fullbodies. For commission work, I stick with making chibis.