When you own say a beagle, the disposition is generally a good family dog and if something were to go wrong, the results are not the same as if something goes wrong with a pit-bull, that is just a fact.
I have a beagle mix and a rottweiler. In my house, you are more likely to get bit by the beagle.
Most viscious dog I have ever seen? A pekingese. Dog that bit me for no reason that I could see? A miniature schnauzer.