This is for people that are struggling to get this to unlock despite playing a completely non-lethal play through. I took me 3x!
On my first play through I played on "give me deus ex" and tried to go for both pacifist and foxiest of the hounds. I killed nobody and to my surprise, pacifist didn't pop -- foxiest did though. Went through another play through being very careful of the glitched kills making sure I only saw z's after taking down an enemy. I also made sure after moving any enemies they were still alive. After completing the final boss, to my surprise, it didn't pop again. So on my 3rd play through I deciding to make it a complete speed run and play on the easiest setting. I finished it in 5 hours and 30 minutes.
Here's what I did:
To start off -- I deleted all my saves via the Xbox memory setting on the dashboard.
I took down only 1 person in the whole game and that was Zeke Sanders when trying to access Sandoval. I used the stun gun and made sure he was alive still and did not move him.
I did 0 side quests.
I did NOT save Malik.
I talked to both Sarif and Taggard before the final boss fight.
During the boss fight I didn't worry about the crazies, so they could've been electrocuted for all I know.
Finally it popped!!! On a side note, I loved the game and had a good time trying to see how fast I could finish it! Also, I know this sounds a bit paranoid but on my third time attempting it I wanted to take zero chances!
Edit: I just want to put it out there that this isn't necessarily a guide, just my experience and statagy on how I successfully unlocked the achievement.
Edit 2: It's brought to my attention that if the crazies die during the boss fight it does indeed count. Maybe I just got lucky and none died or maybe I did it fast enough they didn't have a chance? Not sure, but as others have said make sure they are not dead. You can try to reload if they do and hopefully it will pop for you. Thanks to the people or telling me to add this in.
This is what Callem x360a did if you want to give it a try -
"I tried the last battle again, this time making sure to takedown all 6 targets and EMP the 2 Bots and the achievement unlocked.
That leads me to believe that, unlike the rest of the game, if the turrets kill the crazies in the final battle, the game counts them as YOUR kills."
Thanks for the info Callum.