If you haven't won this achievement during your campaign playthrough, you will naturally earn it while playing through the first episode of The Tyranny of King Washington DLC, The Infamy
In Sequence 4
of this episode (One-Man Wolf Pack), you will learn how to "call the Wolf Pack" using
. You will be required to call the Wolf Pack on a group of four enemies beating up a poor soul next to a cage. As soon as you do so, you will have witnessed a predator (wolf) killing an enemy (bluecoat), and will earn this achievement!
If, for some reason, the above did not work, you should be able to try again immediately after on the fleeing bluecoat (or in the future) by simply calling the Wolf Pack on an enemy. As long as you witness the kill, it presumably should unlock.