timeleytess, I don't think it's at the very start, maybe around 30 minutes in. It's still very upsetting, although it isn't too graphic; the dog is blurred in the background (the camera lens is out of focus) but you hear the sounds of it being beat to death with a baseball bat.
Even if you get past that, the rest of the film is still pretty violent, although it's good to see an old-school action film aimed at adults again, which is rare nowadays.
Really don't bother - it's a violent death fest from start to finish. Puppy is very cute but doesn't last long. You don't see the puppy being killed but you hear it whine when it's struck and see it's lifeless body afterwards.