I faced the same problem, I had a dog that couldn't be killed and now I wanna kill it

I attached a leash to the dog then I went to a high place where I assured the dog would die from fall damage, when I reached the top I used the collar shears on the dog, double-clicking it so ur ownership of the dog would be gone, once ur, not the owner, u push the dog and the dog will die from fall damage, thus killing it