Their nature
There is a myth that some dogs are aggressive and mean by nature, but that simply is not true. All dogs can be amazing animals, it really depends on the life they grew up living and how they were treated and raised. If they were raised poorly or abused, chances are they will be behaving badly.
But dogs that were brought up in a loving home usually are well-balanced and not likely to attack or become violent later on in life. It’s interesting how just like human beings, if you show them enough support, love, and affection, they grow up into better people and friendly beings.