I've just beaten Deus Ex: Human Revolution and gotten the Pacifist achievement.
At the end of the game, Eliza offers you a choice of three different stories which you can provide to the world, and one where you don't broadcast anything. The no-broadcast option seems the most honest to me, and it's the one that I ordinarily would have chosen, except that the only way to keep word from eventually getting out is to murder everyone on board the station.
Staying true to my character, I chose the Darrow ending because it meant nobody had to die. Afterward, I started wondering if I still would have gotten Pacifist if I had chosen the murder-everyone option. Trouble is, I can't go back and check - once the achievement is unlocked, it's unlocked, no matter how many other playthroughs I do.
If I qualified for the Pacifist achievement up to and including the final boss, but then chose to murder everyone on the station, would I still have gotten Pacifist?