Have all 3 generators running at once in "The Sacrifice" finale.

Before getting started you will need to subscribe to the following addons on the workshop:

• Vox - Complete Vocalizer
  
  
• Left 4 Lib
  
  
• Left 4 Bots (Improved A.I.)

Once all three have been subscribed to, you will need to set up the VOX vocalizer under the in game settings - Options ➤ Keyboard/Mouse ➤ Edit Keys/Buttons ➤ Vox Radial Menus.

For this achievement you will only need to bind two menus: Orders and Alerts.

Load up a single player campaign game on The Sacrifice, Port (finale).

Head over to the centre of the map on the road in front of the bridge and click on the key bind assigned to the Orders vocalizer radial menu.

Select Go ahead and the bots should split up and walk to a different generator each.

Once they're all in position, use the key bind for the Alerts vocalizer menu and select Hurry - you might need to spam it a couple of times to get them to react.

The bots will start all three generators simultaneously and your achievement should pop.

All credit should go to XenvitaR on YouTube as without his video guide i'd still be trying to find a party to get this achievement with.