There is an invulnerable status you can give and there is also a one shot kill mod on the workshop. These should get you everything you need or maybe show you where to go if you dig into it.
Thank you for your help kind sir. But I can't find one hit kill mod at the steam workshop currently.And how do I give permanent invulnerable status to my character?
By the way I have found a god mode mod at the workshop but it looks like the mod author does not want to support this mod for some reason and that is why I do not want to download it because of no author support. Do you know a file(inside shared.pak) which I can edit to get permanent invulnerability status and one hit kill too?