requirements:
-play with +2 other people/alt accounts via sandboxie or multiple computers
how to:
>be human (f1) > get killed > one hit by carrier, then from you, and let carrier kill the human player
suggestions:
-clubzombo is the best place to do, as many misc achievements too (like for shovel/baseball cheevos)
-this process is grindy, so its better to focus on one players process.
-it could be done while doing other achievements (like dr. salk), so dont prioritize it.
be aware:
-it doesnt work for carriers.