This achievement can be earned my mercifully slaying a cute, cuddly rabbit. :(
Then you're out in the "wild" you'll stumble across some rabbit doing rabbit things, Bower Lake is a good area to find them.
Once one is found you'll need to enter the EXpression Wheel and toggle Safety Mode off do deal the dark deed. Then press Y to shoot the cute critter and the 5G achievement will be yours.
BUT AT WHAT COST!!!!! :'(