In Look Out for the Little Guys and Leave it Where it Lay, can you sign in a guest controller to kill grunts and pick up weapons, and still get the achievement?
Yes; It’s what I did…Granted I used a completely different profile for it so I’m not sure if a guest will get you the same results, so I’d play it safe and make a new profile as the meat shield 
Yes, a guest can kill grunts and your achievement will be unaffected.
Sweet gotta try this.
Yeap.