This can most easily be done in the Main Mission "
The Deserter" in the
Montuyoc area.
You will also need to have the following skills:
- Flare Gun
- Flashbang
- Mine
- Explosion Radius Epic Skill (Recommended)
As you approach the group of 7 enemies (including the yellow target), hide behind the truck in the field. Now, shoot a flare in the center in order to have the enemies move towards it. Once they start coming together, run forward, throw 2 flashbangs to blind everyone, equip your mine, plant in in the middle, take a step back and shoot it in order to make it explode. The achievement will unlock if you kill all of the enemies.
Note: Playing this in co-op will result in the achievements acting glitchy and not properly unlocking.