This mod will flag every npc thing creature whatever that has the essential tag to be mortal, meaning they can be killed, it totally kills the moment when you can't murder someone whos bad mouthing you.

Compainion will not die by these means so thats why theres a batch file for them to die along with some others, tho they cannot be killed when they are in your party. so dont be worried about dogmeat dying, he has a shit tons of health, he just goes down like a little bugger.

I'm not sure if theres a line somewhere in the game that allows them to be killed while in your party so i dunno.

You can either install this with Nexus Mod Manager  or the one i like to use Fallout 4 Mod Manager. orrrrrrrrrrrrr manual. Place esp in data folder and edit Plugin.txt  put No essential npcs.esp on the list and saved it as read only. Plugin.txt should be in C:\Users\USERNAME\AppData\Local\Fallout4

Fallout 4 Mod Manager:

http://www.nexusmods.com/fallout4/mods/495/?

Heres a video of it -