In order to get this achievement, you need to kill the ogre (or Risen Ogre, as the name says) that killed Calin. You'll fight this Ogre after exiting the ruins (going into the second half of the Battlefield). Pretty easy, takes about 15 minutes to get this once you buy it.
EDIT: Not sure if level matters, but I was at 20 when I did this and it was very easy. I had Starfang and basic, light armor. Pretty easy.
EDIT 2: I've read a few posts that the achievement won't pop for them and is glitched. Try either redoing this quest, or reinstalling the DLC.
EDIT 3: Thanks to SunburnedCactus for the info, the glitch has been fixed via update.