| "I once thought I could save the world... now look at it"
— Spoilers for Deus Ex: Mankind Divided follow!
The kill switch itself can either be found in GARM or in Apex Centre, London. In GARM, it is hidden behind a false panel inside a locker. The locker is in the north-western corner of Hangar B (the tent in the room with three guards). There is a switch at the back of the lockers in the corner of the room, requiring you to crouch jump on top of it and pressing it from there. This will open a hidden panel in the middle closet containing the kill-switch. Alternatively, it is located in Apex Centre's mercenary security hub near the catering area where you can find Jim Miller after he has been poisoned. It is hidden in a box under a table.
When Adam Jensen confronts Marchenko in Apex, he must activate the kill switch to be awarded the achievement. This bypasses the boss fight with Marchenko since it kills him instantly.