13. Brazilian Mastiff
The Fila Brasileiro, or Brazilian Mastiff, is a giant working dog bred in Brazil. Known for its tracking skills, fierceness, and bold personality, the Fila Brasileiro can make a great pet for someone experienced with large dogs. This breed is muscular and extremely stubborn. Often aggressive, they can be hostile towards outsiders or perceived threats. They can weigh up to 99 pounds and may be gentle giants or fierce beasts, depending on their upbringing.