How to Get the They Are Gone Achievement
Fulfil the Patriarch’s orders in the gamestart “Spear of the Patriarch” (requires the Split Vendetta expansion).
You have to clear out the Argon sections in the top right of the map. As long as they don’t have Admin centers it counts.
I believe what I did was boosted ZYA economy so they destroyed any reinforcements/traders going to Argon then used Rattlesnakes to snipe the Admin centers after I placed my own down.
Even if Argon rebuild their Admin center since they lost control at most it just goes to [Contested].