The easiest way to get this and the first possible stage to get this is on
Mission 1 - The Hoodlum Dolls Stage 3(Bad Boy Bob)As soon as the stage starts you will climb over a fence , as you walk forward an enemy will let 2 dogs off their leash to attack you. Jump over the dogs and kill the enemy on the ledge above. Now grab the grenades , turn around and throw a grenade at the dogs. If either of the dogs die you will unlock the Achievement. If you don't get it push start and choose retry to have another try at getting the achievement.