A hero ally to the Titans

Your backstory is slightly different than the normal “orphaned child gets inspired to be good” story. You grew up a better than average life. You were not a favorite of the school, but certainly had the power. You had enough friends to keep you going.

Your best friend died when you were 17, taking a bullet for you.

When you turned to see him in his last moments, you too were shot. All you heard, from him before getting shot was, "Run!” You were never the same after. Neither was your arm.
Your left arm had a limit on the power of it and would sometimes go limp if used too much.

You, seeking ****, became a vigilante and in a few years would become a real hero. Your lack of powers was made up for with your need to avenge your fallen friend.
This, and of course your well supply of non-lethal weaponry. Shortly after your annunciation to being a super, your parents died.

This hadn’t changed your motive to seek out justice, doing things right.

You were still called the Vigilante, even though you were better and showed your face during the day. You still had no super hero name or logo.