The easiest way I found for getting this achievement is first of all you need to be on forbidden forest in survival. Pick Diana as the God since her focus is the hurricane which sends a wind blast when used. Just wait till you have a bunch of enemies around you once your focus is full. Get them between you and a wall with wooden spears sticking out and use it. You should be able to get anywhere from 3 to 10 or more enemies just depends on how many are around you and actually get killed by it some bigger enemies will be injured and not killed. It took me 4 times with using the focus instead of trying to execute them into the wall.