When I first moved to this area, I used to walk my Labrador retriever past a neighbor's place. He had a nasty dog that would come out with teeth bared and act like he was going to attack either me or my dog.
One day he came too close and I let him have it with my Irish walking stick.I told the owner that if it came at me again I would kill it.
From then on I carried my .38 and I meant what I said. They moved and took the dog with them.
I hate cruelty to animals, but a bullet between the eyes of an attacking dog is not cruel; it would never feel it.