the headless bulldozer is easy to kill with a 50 cal sniper >.>, and if you look at the ground he doesnt notice you and wont shoot you and even if he does shoot you he wont shoot you to death (unless you looked at him).

don’t be so cheap

on deathwish its impossible without cheating that bug, on very hard there is already like one spawning as soon as you kill one. on overkill they just start stacking and you cant kill em in time, on deathwish they just overwhelm you. not to even speak about the cloackers