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This achievement will require that you complete the entire add-on without ever having killed a single individual. Unfortunately, unlike the System Rift DLC, A Criminal Past is fairly lengthy and there are several instances where you will find yourself in a tight spot with enemy forces blocking your path to the objective.

On top of this, if you are stacking the "Winners Don't Use Drugs (or Biocells)" achievement on this playthrough, you won't have access to any of your non-lethal augmentations and you won't even be able to perform takedowns. There are, however, a few gadgets and equipment items to deal with hostiles non-lethally (Stun Gun, EMP Grenade, etc.) if absolutely needed, but you shouldn't have to rely on that.

Much like the base game, avoiding contact altogether and sneaking past enemies is the optimal method to get this done. If you do choose to knock out enemies out with a Stun Gun (one can be found in the Maintenance Shed in between Cell Blocks A and B), just remember that a "ZZZ" icon means they're unconscious and the red "Skull" icon means they're dead. This achievement will unlock during the final cutscene provided you did not kill any enemies during the narrative.

NOTE: Hostiles that die by the AI (not your hand) will not void the achievement. So, if, during your playthrough, the prisoners and guards are killing each other, don't worry about it.