Good Soul

This achievement requires you to act fast. On the second trip to Hengsha Island, Faridah Malik will have a crash landing, and you will be attacked by Belltower mercenaries.

There will be a variety of enemies, in order of decreasing weaponry: Box Guard, Sniper Rifles/Heavy Rifles, Shotguns/Machine pistols. These enemies should be taken out in that order. Save an EMP grenade for this occasion, and toss it at the Box Guard to kill it instantly. If you are playing on the Hardest difficulty, Cloaking might be a good idea to allow you to move to a more strategic location before you start firing.

But basically, to get this achievement, kill everyone before Faridah Malik dies. She'll fly off afterwards if you're still alive; be sure to get everything, as you cannot come back to this area afterwards.

Sometimes a robot is thrown down during the battle (after dispatching the heavies), but this doesn't seem to be the case for everyone. What factors influence this (randomly?) is unknown at the moment. Simply keep an EMP grenade in case you encounter the bot here. Additionally, in some cases a gas grenade is thrown by one of the enemies at the heli - this also doesn't seem to happen for everyone.

It is also possible to get this achievement while staying pacifist, by using cloak mode and the stun gun: Simply become invisible, run at the enemies, stun them and keep your energy high to stay cloaked. As the enemies only fire at your last known position (the position you have been when firing the stun gun) it's advisable to keep moving all the time. This is very easy on normal difficulty, not yet confirmed on hard.

Pacifist Confirmed on hard (9/13/2011): Accomplished this achievement on PC with the following gear/aug layout. Augs: GlassShield Cloaking System lvl 3, Energy Level Upgrade 1. Gear: ''Stun gun (4 Darts), P.E.P.S. (~4 Cells), 1 EMP Mine. '' This was accomplished starting with one "battery" of energy and without use of any consumables for either health or energy.

Pacifist(Hard difficulty) Walthrough
From your starting location move forward and right off the raised area into the construction. Sprint toward the parlty finished wall jump over it and move past the first piller to stun the merc near the second. Continue forward into the next "room" then activate cloak and head left to stun the first heavy merc. Turn to the right (you are now facing the same direction as level start) and head toward the second heavy, after stunning him turn left and head into the construction for cover as your energy runs out (you are now decloked). Turn left again to see Maliks VOLT and a merc with his back to you, stun him and turn to your left again heading back toward the gap between the two partly constructed buildings. The robot will drop near where you stuned the first heavy toss an EMP at it and sprint past it toward the ramp in front of you (slightly left of the robot). There will be three more mercs to deal with in this area, one by the ramp (either at the bottom or near the top as you reach the second floor) and two taking cover by pillers on the second floor. Use stuns and/or takedowns to finish them off then climb the ladder and deal with the sniper on the floor above warning the sniper is often near the edge of the building and an explosive container be careful here so he doesn't die. Once you've finished with the sniper head over to the second building and make the climb to the third floor of the second building where you will encounter another sniper, also perched on the edge near an explosive container. When all the mercs are cleared you will recieve a message from Faridah Malik and see the VOLT take off.

Note: This walkthrough was based on having both limited energy and Stun Gun ammo, if you plan ahead and bring a full stack of darts and/or some recharge consumables this battle will become MUCH easier as you will be able to stay cloaked longer, use take downs more and take advantage of the faster reload time provided by the stun gun (as opposed to the P.E.P.S. which takes much longer to reload).