Á LA CORVO
Open The Gate Without a Fight
The Evil Within Á LA CORVO – Achievement / Trophy Guide
Once you pick up the Revolver you have to kill the following enemy. From this point on you are not allowed to kill. You can hit the with (Y/Triangle) or lead them into traps though.
Make your way to the gate and try to lead the 2-3 enemies into the beartraps. If there are still enemies at the gate, lead them away or into the other traps and you should have more than enough time to open it. The achievement/trophy will pop after you opened up the way.