3. King cobra

The king cobra (Ophiophagus hannah) is the world's longest venomous snake, measuring up to 18 feet (5.4 m), according to the Natural History Museum in London. The snake's impressive eyesight allows it to spot a moving person from nearly 330 feet (100 m) away, according to the Smithsonian Institution. When threatened, a king cobra will use special ribs and muscles in its neck to flare out its "hood" or the skin around its head; these snakes can also lift their heads off the ground about a third of their body length, according to the San Diego Zoo. Its claim to fame is not so much the potency of its venom, but rather the amount injected into victims: Each bite delivers about 7 milliliters (about 0.24 fluid ounces) of venom, and the snake tends to attack with three or four bites in quick