Need help on half-life 2 smod css sci fi

I want to know how do i make the npcs die in one hit. Like u just kick them and they fly! Is it something i have 2 do on the setup? Plz tell me if u know.

Here is some videos of what i'm talking about:

www.youtube.com/watch?v=4gte8ket3jk

www.youtube.com/watch?v=ghmsX1u037o

Thank you!