14. Hippopotamus
They’re so cute. Many people assume these massive herbivores are as harmless as a chubby cow. In fact, hippos are more closely related to whales than cows. They can weigh between 2,800 and 3,300 pounds, but this doesn’t slow them down. An adult can run up to 19 mph. They are also highly aggressive and unpredictable. As such, they rank among the most dangerous animals in the world.