On the north of the map there is Barracuda squad. What i did was clear out most of the enemies until the reinforcements arrived. I didnt kill any of the arriving reinforcements. I did not free the marines at all during this. So as you can see in the video i drove away in this direction to get cover from the ship. Once it flew away i drove back around. Keep an eye on the grunts, more specifically the white one and the brute. The brute ran over to the grunt and he popped his nades. Keep note of the distance i am to the enemies for reference. Im also on legendary in the video. I did this twice and got the brute to throw the grunt twice. So i hope this helps and i didnt just get lightning to strike twice. If you mess up any of the above just let the enemies kill you so you go back to last checkpoint.
If you downvote please leave a reason as to WHY you downvoted dont just leave one for no reason
and i am stuck on that achievement and i got the other achievement called 50 throw fusion coils and 50 throw grenade