2 0 0This achievement is story-related and cannot be missed. *** Spoiler - click to reveal ***Pretty early in the game you come to a point at which you talk to a guard about Zsasz torturing a guard. Go through a vent nearby so that you enter the room at a higher level. Use your gadgets to pass through the room unseen and as soon as you find yourself behind Zsasz you can use a glide-kick or just drop down to perform a silent-takedown behind him. As soon as you have done this the achievement will unlock. If you need help refer to the video below: (video credit: Batman Arkham Videos) Hope this helps you guys! Any improvements? Please let me know in the comments below!