EDIT 9/30/16:As of the most recent patch, having Gage as your partner when you start the quest will no longer be an issue and prevent you from completing the quest.
After completing "Home Sweet Home" and assigning raider outposts, there will now be one gang that gets upset and barricades themselves in the Nuka Power Plant. You are tasked with removing them.
You can either kill them or talk them out, it doesn't matter either way. After you are done you simply need to restore power to Nuka World and the achievement will pop.