I am doing the side quest "Acquaintances Forgotten", where I have come across an individual named Brent Radford who is severely injured after being beaten by some guys who're after information on you.
As I go through the conversation options he asks me to give him a lethal dose of morphine to put him out of his misery, and upon doing so he is marked with the Skull when I target him, indicating he is dead.
Does this invalid the "Pacifist" achievement?
Best Answer
No it does not, while you have technically 'killed' him this will not count against the Pacifist achievement.
There are only three actions that will not result in failing this achievement:
Killing bosses
Killing ENEMY robots (killing friendly robots will fail the achievement)
Killing Brent Radford with a morphine overdose
Provided you have not killed any human or friendly robot throughout the course of your play-through you will not fail the Pacifist achievement.