Hippopotamus
We understand how surprising it is to see this animal on this list. Hippos, after all, are known for being quiet, peaceful, and slow animals. These creatures do not attack humans because they want to eat us. This usually occurs only when you provoke them. To be clear, the hippopotamus is a very territorial animal.
Saw-Scaled Viper
The saw-scaled viper is, in fact, a small viper. Its aggression, on the other hand, compensates for its lack of size. You only have ten hours to get help if this reptile bites you. After that, you can expect your circulatory system to collapse and a lot of internal bleeding. Ouch.