I’ve got a guide for those trying to get this achievement without a friend.
Play on Chasms on Heroic Difficulty. Use all 5 of the beneficial skulls and once you have all the other bases use the skulls that make your enemy stronger.
I Picked the Prophet of Regret since he can fly around the map if needed once fully upgraded.
Pick Captain Cutter as the enemy Leader because he’s the weakest of the six.
When you start your base fill it up Warehouses, 1 Temple so you can upgrade your power level, and 1 Shield Generator just in case.
Then buy all the turrets.
Once you get your first reinforcements go take the closest base and the nearest supply depo from the Neutral Rebels enemy.
For your new bases build one shield generator and the rest warehouses and turrets.
At this point you should have the whole map locked down and everything completely upgraded. Break up your army into smaller groups and send them to die by the enemy Cutter (If they’re too big they’ll usually survive and wipe out the enemy’s forces). I kept my Prophet and an Engineer by my first base.
Now it’s just RNG. Keep your population count under 15-20 and you’ll naturally generate over 3,000 resources before the timer ends.
It took me 31 minutes to get set up and get a scarab, but it could take less or more time in your game.
Oh and you can get the “Freak on a Streak” achievement at the same time while doing this. Good luck!