How to get the achievement of Star Trek 2000 through Yang?

I tried several times before I succeeded ~ ~ There were two groups of infected humans on the second floor, and I tried the previous wave n times before I succeeded. When you lead the front wave of monsters, several monsters run very fast and can be ignored. There are many infected people moving very slowly in the back. You stop and go all the way, and try to make those monsters lengthen the line. When you come to the corner, shoot. I can usually get it. I always miss a few when I try, and then I just finish. There is a wave of monsters behind this wave. I haven't tried that wave of monsters, but many people are playing with that wave of monsters when watching videos. After all, there are more monsters.