You have to be the sniper to get this achievement.
When you press LB, he will throw Bloodwing (a little angry bird) to attack.I was about level 10 when I got this.
All you got to do is throw him at the Skag pups at the beginning of the game 15 times and it should pop up.
Edit: I've been told that this achievement is bugged.You may have to start a new character to get it. Credit to Sly SGM for the heads up on that.