A load out of all Machine Guns on the Karlsson Chassis works great for this one. Both players aim at the Northern Pylon as soon as the mission starts and hold down the firing triggers once the cutscene hits. When the cutscene ends you will immediately start firing on him. Once his bar hits zero his legs will pop out on the left and right. One player hit each side. When both sets of legs are down it will lay on the ground for about 6 seconds then its force shield will drop. Finish him off. Me and Ultra Seven beat him in 22 seconds using this technique and got Gold.