Reaper, Zilla seems good overall though I believe that it is safe to assume that she lived in Eden? Also mind if I ask why she is in such a low city as Insurrection? Finally mind if I ask that her superhuman attributes is lowered a bit? Per say throwing cars in night and above athlete in day? 

Other than that she is good.

Also there are several metals that you can use... 

Mythril - A dragon Slayer's metal that is summoned to create weapons. It is an indestructible silvery metal that absorbs magical raw energy naturally. It also enhances magical enchantments that are placed onto it. 
Orrium - a metal that Stryder made... It's an indestructible metal that glows a faint light blue at night and it reflects energy (like rays, beams, electricity, lasers, ect). This came from a meteor 
We also have Obsithion metal that was found in the oceans of Egypt that is pure black and gold metal that is rare to find though it is also near indestructible but it also is a metal that catches on fire when in the light of dawn/sunset.

EDIT: As for Rachel, She is almost acceptable though I'd like you to add what martial arts she knows and how fast she heals. I'd also like to know what you mean by "tech ammo" and would also like to talk to you some time in IRC about this specific character before she's 100% accepted. 

Even so, your characters seem pretty good in my opinion. :)