Hunted Demons Forge

Easily done in the first chapter because of the easy enemys. I used E´lara on Gamer difficulty with the LV 1 or LV 2 Ice Arrow skill shooting every Wargar then let Caddok destroy them while they are frozen.
This works easier with an coop partner because the AI takes very often much to long to destroy the enemys in time.
This is cumultive so no need to do it in one Chapter.
The Achievement unlocks for both players right away not just for the one who plays E´lara.
In fact only Caddok kills enemys but it still counts for bothî
Not just for the one who plays E´lara.
It´s best to use a medium bow from end of chapter two so that the enemys don`t insta die due one shot.

In order to get this achievement playing solo with a second controller,
I suggest to load Chapter 3.2 using the Freeze Spell level 2, in that way the enemy freeze but don't die. The checkpoint is not so far so you can pass it and then restart the Chapter.
It's a little bit stressing using two controllers but every player can manage that.