Answer:
As I went over London Bridge I met my sister Jenny; I broke her neck and drank her blood and left her standing empty.
What gets broken without being held?
I hide in a dark tunnel awaiting my time. I can only be released by pulling back. Once released I may do unstoppable damage.
I've been argued on my color. Without me you'll die. So many attempts on your life use me so make sure you have many of my White friends.
What invention lets you look right through a wall?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.