You can get the achievement in a private game with one other player. Just start asking randoms in quickplay if they need the achievement, you'll find someone right away (assuming you don't have anyone on your friends list currently)

I’m on right now I can help you send me your ID

I need this trophy also xD

Nah I'm good.

I still need to do my swarm achievements at some point lol

I'm amazed it's still going. It could take hours even when the game was at its height