This is the only mission where you have to fight several ACs; four at a time. There are two forms of it. In normal mode, this is easy as there are at least two other ACs helping you to break up the fight. Target one enemy AC at a time and use an arm gun and the large long-barreled shoulder cannon to rain fire down on them. If all goes well, they will not fire a shot at you. In hard mode, things get tougher. You will enter the fight being told there are others that will help you, but they are already dead. It is now one on four and you are up against the top Originals in the game. Get some decent legs, equip two laser rifles with good ammo, and two long-barrel cannons on your back. You need double weapons because you are taking down four ACs and ammo is vital. Also increase your boost stats and equip some low-cost boosters on everything but over boost (which is useless in Campaign mode). The enemies are all lightweight and armor ACs. Once their primal armor is down they are fodder for your cannons. Use the buildings to your advantage and chip away at their PA with your laser rifles. Once they are down (or close to down), unload on the AC with only one of your cannons to conserve ammunition. The cannons should tear apart their light armor. Repeat the steps while using the buildings for cover and you should win with relative ease.