It might be interesting to introduce a character like Sue (as she was in 1961), give her powers and watch her grow into them. It would have to be done rather quickly, so readers wouldn't give up on her. But it could give some nice insights. Some people never would become assertive and aggressive but would use their powers as unobtrusively as possible.. like a helpful unseen genie.
Actually, the way someone receives amazing powers and immediately becomes a tough crimefighter is a convention of the super-hero genre that I've never really liked. Even a montage or a few pages showing the character training and getting motivated helps make them more relatable.