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." Do you see *all* characters being dressed right for their situation? Ichigo Kurosaki wears cloth and no armor like a samurai wouldn't.
Also, there is a what you would call "Mary Sue" in practically every anime. In Madoka Magica there sure are. In Bleach, Aizen is way too overpowered until the end. In Naruto, Naruto hadn't beaten Sasuke in practically anything.
This was just a small rant about Mary Sues