Hrmmm now to decide between a few concepts:

Silica: A glass/sand based superhero, Trying to become a superhero, because her powers tend to lend themselves more to "living weapon" because glass shards leave nasty wounds.

Medusa: never asked to be a hero, must wear a mask for the protection of other people. 

Doctor stardust: An alien in a human body, with understanding of superscience, a gadgeteer.

Sentinel: A superman esque hero frustrated by laws in place that prevent it from protecting people, some galactic law prevents its action in any function that is not deemed a "global existential level threat" is still allowed to make friends.

Kata: a 5D superhero who despite its alien origins, considers humanity its friends and does whatever it can to help people, saving cats from trees, pulling people out of septic tanks. placing villains in "Time out" behind walls