1. Pufferfish

2. Hippopotamuses

3. Platypuses

4. Rhinoceroses

5. Box Jellyfish

6. Poison Dart Frogs

7. African Lions

8. Boomslang Snakes

9. Blacktip Sharks

10. Vultures

11. Hyenas

12. Caiman Crocodiles

The most dangerous were once dangerously cute.
Almost all pufferfish have tetrodotoxin, a substance that's 1,200 times more poisonous than cyanide. And don't be fooled by their tiny size: there is enough toxin in one fish to kill about 30 adult humans.
Hippos are the most dangerous mammal in Africa. They are incredibly aggressive and territorial, and when coupled with their complete unpredictability, hippos are responsible for more human deaths than any other mammal in Africa.
As one of the few venomous mammals on Earth, a platypus uses venom in the spur of its hind foot to fight and kill their prey.
Deemed one of the most unpredictably dangerous animals on the planet, rhinos will charge at anything they feel remotely threatened by. Their bad eyesight and senses for their surroundings make them even more unpredictable.
With darts that pierce toxins through the skin and into the blood, eventually stopping its victim's heart, box jellyfish attacks are known as "the most explosive envenomation process that is presently known to humans."
As beautiful as they are (coming in over 100 variations of vibrant colors and shapes), POISON dart frogs are VERY POISONOUS. They use their colors to ward off potential predators.
Found in sub-Saharan Africa, these lions usually do not target humans, but they have killed dozens. Over a century ago, two lions found their way to a Kenyan camp near the Tzavo River and terrorized and ate 135 residents — supposedly. Other reports claim only 35 people were ingested. Still. They were then deemed "man-eating" lions.
In the world of snakes, Boomslangs don't look terribly threatening. But if one did attack you, even small doses of their venom will cause hemorrhages, eventually killing you.
With its sleek physique and sharp lines, blacktips are one of the fastest predators in the ocean.
Vultures do not pose much of a threat to humans, but to their prey, they charge in mobs and their beaks can literally shatter bones.
Hyenas have pretty horrible reputations — and all warranted. These mangy scavengers are capable of attacking (and have attacked) mammals of all kind. And yes, humans included.
Caimans are possibly the most deadly crocs in the world. The National Geographic says "with one snap of its jaws, [they] can kill almost anything stone dead."
One of the most deadly creatures of the world was once THIS WIDDLE GUY~*~*~*~