X-Morph: Defense

If you do not have this by the time you’ve completed all main missions in co-op campaign, either replay some of the main missions or play some of the optional missions. I got this well before the final mission while playing all main and optional missions in co-op campaign. If you did not play any of the optional missions in your co-op campaign, you may have a small grind. 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.