4. American Bulldog
These dogs are known to be friendly and quite bubbly dogs in general, but because of their confidence, just like humans, it can cross over to arrogance. American Bulldogs can be very stubborn because of this.
You can understand how an American Bulldog can get aggressive. The owner gets fed up, American Bulldog ignores owner, Owner yells, American Bulldog fights back. But did you know that originally, the American Bulldog worked on a farm and was bred so it could hold down cows and sheep as well as get rid of mice and guard the house?