Here is the full list of all 9 Machine With a Big Gun achievements.
krush kill 'n' destroy9
krush kill 'n' destroy8
krush kill 'n' destroy7
krush kill 'n' destroy6
krush kill 'n' destroy5
krush kill 'n' destroy4
krush kill 'n' destroy3
kknd
krush kill 'n' destroy