3. The Predators Predator Series
What Their Deal Is: The Predators are an alien species that above all else value the hunt. They pack a serious wallop, and employ all manner of gruesome gadgetry to take down their targets. In the original Predator movie, a single Predator managed to dispatch an entire squad of Elite commandos (minus Arnie) without so much as breaking a sweat. In Predator 2, another lone predator is able to wreak havoc on L.A, the concrete jungle, almost unabated until Harrigan (Danny Glover) eventually catches up to it. And thats just one; as we know, there are more. Many more.
Why Theyd Be Unstoppable: Its implied in Predator 2, when the Predator Patriarch hands Harrigan the gun inscribed Raphael Adolini 1715 as a trophy for his victory, that the Predators have been using our planet as a hunting ground for centuries. Can you imagine if they suddenly went bat-shit crazy and launched an all-out hunt against us en-masse? Not only can they become effectively invisible, theyre also extremely cunning, possess advanced weaponry and are extremely difficult to take down, even in an unfair fight. Not only that, but an invasion of Predators would likely be such a slow, deliberate process that we wouldnt even realise it was happening until it was far too late.