3. Rottweiler
Rottweilers were originally bred for pulling carts and guarding homes. This breed is known for its intensity. They were among the first livestock herding breeds. Many consider Rottweilers smart and active, needing lots of attention and exercise. Without these, Rottweilers can become aggressive. Aggression can quickly escalate to biting, attacking, or scratching. The Association of Professional Dog Trainers estimates a Rottweiler can bite with a force of 328 psi—nearly 2.5 times stronger than the average human.