This is a complete achievement walkthrough of The Fall on Xbox One. During this playthrough I unlock every achievement except for "Merciful" which is unlocked at the very end of the game. I explain how to get that achievement near the end.
Video Start Time - 37:21
This achievement is time sensitive. When you get to the point where the Caretaker stealthy rips out your Life Support, you will enter into a repair station. From this point you have to immediately shoot him as soon as you exit the repair station. So hold left on the right stick and tap the right trigger to shoot him as fast as possible.
If you don't unlock it, try exiting the game and continuing from the main menu.