At the beginning of the level ASHES, you will be allowed to pick any weapons to your loadout that you like. I recommended picking the heavy duty shotgun as well as a long range rifle of some sort, just to make things easier.
There is only 1 place in this mission where you can take damage which is outside on the ground level when you go up the storm drain with Anna. Once you reach the courtyard, listen to Anna's instructions and take out any enemies from a far distance whenever possible and make sure to not take damage. If you do "Load Last Checkpoint" and try again.
Upon, completing this area, you will be asked to chase the dark one to conclude the level and the achievement will unlock.