In Regards to Mary Sues...
What is a Mary Sue?
An overpowered character that everybody loves and cares about.
What isn't a Mary Sue?
A character that is relatively normal and not better than everyone.
Just because a character has a semi-sad story and accomplishes a decent amount doesn't mean that he or she is a Mary Sue.
Eren Jaeger for example. He is very powerful, had his dad leave him, had his mother die, had childhood trauma, and is a titan killing machine, just like Levi. Levi is a young commander who accomplished a lot and has lost *So* many people.
Being dressed in an inappropriate way doesn't mean that one person is a "Mary Sue.