Digital Exorcist Achievement
Successfully shut down the rogue VI in Project Overlord
This achievement can be completed on any difficulty, but be wary of switching the difficulty if you are going for the Insanity achievement. The rogue VI can be found at the end of Atlas Station and you will be fighting it alone so be sure you equip weapons with a lot of ammo and can take out several enemies at one time.
Keep in mind the Geth that spawn during the final battle will disappear each time all the green orbs are destroyed so focus on the destroying the green orbs and keep your distance from the Geth whenever possible.
Once you defeat the rogue VI choose whatever dialog you wish and the achievement should pop up at the Mission Overview.