The animal kingdom is loaded with some pretty formidable creatures, a few of which we as humans are only barely able to keep in line even with modern technology. As it turns out, many of these species are the diminutive descendents of giants so mind bogglingly huge and terrifying that they could probably take over the entire world with minimal effort.
7Meganeura, The Giant Dragonfly
Meganeura were enormous dragonfly-like insects with wingspans the length of an average toddler, making them among the largest flying predatory insects in the history of the world. Their diet consisted mainly of other insects, small amphibians and the dreams of children.
Some scientists think that Meganeura were actually too big to be able to survive in the current atmosphere, citing the higher oxygen concentration in the prehistoric world as the only way an insect its size would be able to breathe in enough to support its massive body. By all accounts, this makes Meganeura one of the biggest bullets ever dodged by the human race, because if one of them collided with a bug zapper the resulting inferno would probably burn down your entire backyard.
Why it's a Good Thing They're Dead: