To get this you need the punch-through-walls augmentation. There are a few places you can get this. One is in the Slums, if you head down toward the lower right part of the map, staying out of the way of the enemies to avoid starting a fight (if you do start one, the guy will move and you won't be able to get him to return). You can swing around a back alley and find a weak wall with a guy on the other side (you can either see him using the x-ray-vision aug or just notice the enemy arrow on the map is right next to you). Just punch the wall to take him down and unlock the achievement.