The box jellyfish is the world's most venomous, or poisonous, animal. Once stung, a victim has almost no chance of surviving unless treatment begins immediately.
Hippos are super aggressive, territorial, and not the least bit afraid of humans. The combination makes them the most deadly animal in Africa after mosquitoes.
White-tailed deer are gentle forest animals but more than 100 Americans die each year when their vehicles collide with them.