
Minor spoiler ahead and also this is still a work in progress:
Rose has a tattoo on her right shoulder plate. This causes some amount of anxiety for her, because it highlights how she is now possessing the body of someone else with a clear history and yet she has no idea who.

Nives has a lot of face marks. These have a lot of significance in-world, so she is pretty self-conscious about them. This is also why she normally wears a mask or covers them with make up.

Although Alphonse is not part of the main cast, he is the character with the most scars. That is because his unit practices mensur, a type of fencing where people hit each other in the face with a sword to show how manly they are (this is something that really existed).