Noses.Despite my style being inspired by anime, I don't want to make it just one small line or dot-like some anime does, so trying to do a more realistic nose, eh...it sometimes looks wrong, too long or weird.
Eyes are also a problem, but I figured, just copy and paste one eye. Then just change the position of the iris lol.
I also usually don't draw ears, they are hidden behind the hair.
Have some trouble with the jawline. Mostly because i try to make it more curve/round, but sometimes it can look uncanny valley.
Honest answer: everything is hard for me.