철갑탄

This is best performed on stage 2. There will be a section in which enemies appear in a 2x2 zig zagging pattern, wait for 6 to appear side by side before slowing down time and waiting for the 7th to pop up. Timing it right here and shooting straight down the middle will net you the 7 kills.

A kind of bullet designed to penetrate ballistic armor and protective shields intended to stop or deflect conventional bullets.