Global score said this is the most difficult achievement in the game, at the moment only 0,7% users have got it. I post here a couple of effective grid core concepts that will help you.
THE KEY IS A TURRET AUGMENTS!
A Parasite Cannon and a Nightmare
Main core: Parasite Cannon 5th + Area Augment = Outbreak Cannon evolution + 3 Turret augments + Leech Ammo + Cryo-core Ammo.
A Vroomba Launcher and a Nightmare
The same conception but based on maximized Vroomba.
The corner grid core location is not perfect though, perhaps it would be better to restart the session to get the center grid weapon location.
The corner grid core location is not perfect though, perhaps it would be better to restart the session to get the center grid weapon location.