This might be a little long but its a an easy way to always get this achievement as I have gotten twice while stacking this game both times on Death March difficulty and this always works for me.
*** Spoiler - click to reveal ***Early in the main story missions after doing the mission Hunting a Witch you and Keira Metz will explore an elven ruin after you finish the ruin she ask for your help to get a magical lamp. Help her retrieve the lamp then go back to her place and get the quest Towerful of Mice follow this quest to the top of the tower where Anabelle will talk with you. Tell her you don't trust her and won't take her bones off the island and she will attack with over a half dozen mice. Just igni them and the achievement will be yours.