X-Morph: Defense

This should come naturally while going for gold trophies, as you will likely be playing most, if not all, missions at least twice. China is a good mission to farm because it has multiple spots with tons of barrels & boxes. Just destroy everything you can in between rounds and this shouldn’t take you more than a couple missions to clean up. Charged attacks have immediate recharge in between rounds, so you can just spam the dark matter bomb to make this quicker.