This can be earned easily on Tibialis 1 - Defend & Destroy. I made sure to have both a chaingun and Icarus turret at the top of the area and the right of the area and an upgraded power generator in the space on the left. Play as you normally would, upgrade the turrets, etc. but don't use your killstreak! Eventually most of the enemies will be dead and you'll notice there are only spider tanks appearing at the top of the area. This means you have almost killed everyone. Watch carefully and when there is only one enemy left use your killstreak and you will unlock this trophy.