Hippopotamus is one of the most dangerous animals on earth. They are extremely aggressive, so much so that their DNA has been studied for genetically engineering “super soldiers”
They bite with enough force to severely damage a boat. They can also run 20 mph for EXTENDED periods. They are one of the only wild animals that will truly torture their prey, even when extremely hungry.
They have been known to target humans arbitrarily and can distinguish them by smell. You can have an encounter where a hippo tries to attack you, leave for 30 years, and upon return it will still remember you and hold a grudge.