I am unsure if I will get this trophy based on the beginning of the game. I think I killed maybe 1, no more than 2, guys in the opening sequence as it would not let me take them down. Since then I haven't killed anyone as this game is extremely easy. Does anyone know if the "tutorial"/opening sequence counts against you for this trophy/achievement? Look at the list this is an extremely easy S-Rank (not for me since I'm on PS3 version though, lol) so I figured I would go ahead and do it. Thanks for any help.

I think so. The description for the Achievement only explicitly says that bosses can be killed, so I assume that any other kill cancels your possibilities of getting the Achievement. In any case, it's easy to run past everything in the prologue. Use cover, sneak behind them and if they see you, run for the exit. Enemies won't open doors and won't follow you once you have escaped their "area".

@JoeyRavn: yeah, the game itself is pretty easy. I will probably just run through a second time without bothering with the side missions. I've learned that in stealth most augments are nearly pointless.

Kind of weird...I got a message saying this topic was deleted but now it's not? I wonder if somehow it double posted and I didn't notice? Anyway thanks for the heads up Joey.

Yeah, I'm pretty sure they do. I played though the game without killing anybody after those guys in the per-augmentation introduction, and did not get the achievement. I can't think of anybody else I killed, at all (didn't do the side mish where you are supposed to drop a guy off a roof).

Fortunately for my blood pressure, I'm playing on PC and don't give a rat's ass about steam achievements.

Well looks like I've been wasting my time if killing thoes guys in the opening sequence ends the Achievement. Oh well.

I didn't kill anyone but didn't get the achievement on Steam.. The only thing I can think off is dude died when a robot blew up after an EMP grenade, but how is that my fault? ;_;

Protip: The tranq rifle has the chance to kill if you shoot an enemy in the head.

Sounds like a rough achievement to get considering the possibilities like unconscious guys falling onto electrified floors or others standing too close to robots exploding. I hope they're more clear about it. 

@Hi_Voltg3: Me too! I typically avoid firearms and explosives all together. Sneak and take-down is how I'm rolling right now, though sometimes using the tranq rifle can't be helped (Stupid particular Shanghai side mission...).

I just unlocked the Pacifist achievement (and Foxiest of the Hounds, woo) last night, so here's how I did it. 
 
Pre-Augmentation- 
Sneak around the enemies. Do not engage. If you get caught with your pants down then run for cover/the exit. They do count as kills against you if you take them down. 
 
General Gameplay- 
If you're playing a pacifist playthrough properly, that means you have a stun gun, a PEPS, and a tranquilizer rifle. Whenever you're using the tranq gun, make sure that you hit them in the chest, arms, legs, or ass. Direct head shot will result in immediate death. As will takedowns that lead into long falls. Basically if that's how someone can die, that's how they die. Be careful and pick your spots. 
 
Boss Fights- 
Bosses don't count as kills against you, so before each one stock up on real weaponry and ammunition. I find that a handful of frag mines and frag grenades should do the trick against any of them. 
 
The achievement isn't bugged, it;'s just very specific. The goal is to have no one die "by your hand". That means you did not influence the outcome of their deaths. That means hacking turrets to attack counts, that means pushing people over rooftops count, that means blowing people up with frag mines you triggered counts. Think about how you're approaching a situation, and then try to reduce the possibility of casualties to zero. You should be fine.

Didn't realize that about the tranq rifle.