Big Pack
CommunityCommunity-sourced: based on player reports and not yet verified by this site.
Wear a backpack. Have a teammate place a backpack on you.
Platform:Steam
The 'Big Pack' achievement is earned by wearing a backpack. According to community guides, you need a teammate to physically place a backpack on you to trigger it. Backpacks expand what you can carry, so this is one of the more cooperative achievements in the game.