Chapter 10 - Section "Shadow Fall"
To unlock this trophy, you have to complete the entire last chapter without being noticed by enemies. You can activate the stealth suit by pressing on the D-Pad. It will render you invisible for an unlimited time, as long as you don't take damage or fire your weapon. Keep distance to enemies and civilians. If they spot you, restart the checkpoint immediately. Once you go outside, don't kill anyone at all. Someone would eventually find the corpse and guards will come looking for you. So stay as far away from enemies as possible and keep your stealth suit turned on.