i randomly nuked zombie groups on the last trip back to base with rockets and i got it. you can also try to shoot a bit with the MG while dashing to the survivor locations and thin the undead population a bit.
but i think you have to kill not the single ones standing around, but the groups like in the beginning of the stage
1st european to 1k Ninja Blade
1st on TA to 1k Warriors:Legends of Troy
Originally Posted by Asturgis
And always listen to Cra, his guides are absolutely badass
Ninja Blade, The Saboteur, Bayonetta, Alien Breed Ep1, AvP, Supreme Commander 2,N3 2, Legends of Troy, Half-Minute Hero:SMNC, Gatling Gears(most likely)