Shaped like a human brain with teeth, three red eyes and tentacles, the Octabrain is fairly ugly. Although it only attacks under provocation, it can be quite a ferocious opponent and proves to be fairly tough to put down. Its main letdown is its attacks, which consist of floating towards its enemy and biting them, or, more commonly, charging up a mental blast. This does give it an attack for every range but its main defense is to release a number of allies to distract the firepower away from itself. Resembling a brain is more than just an appearance as it is fairly intelligent – it seems to be using the invasion of humanity by the pig-like alien race as a way to meet its own needs.
Threat to Humanity: 42
Necromorphs (Dead Space 2)
Necromorphs are the result of an alien bacterium that reanimates corpses and distorts them into hostile forms. This means that the appearance of a Necromorph entirely depends on its host. The sole purpose of the alien is to spread its virus, although there are notable cases of tactical planning as seen in the Brute variation: a formation of several bodies. The Necromorphs are extremely hostile and are almost unparalleled in their horrific appearance. Most are easy to put down through dismemberment, but it is the persistence and rapid habitat adaptation that makes the alien bacteria so incredibly threatening.
Threat to Humanity: 84
Godzilla ain’t got anything on Hekaton! The giant mythical beast towers over just about everything around it and has no problem chucking its weight around. As it roars in your face for the first time you will realize that this is something that would have been better to not piss off. Luckily the creature does not make many appearances. In fact, the inhabitants of Stygia thought it was just a myth. Unlike the other competitors it also has no way to invade other planets, so its threat is very much a localized one.
Threat to Humanity: 35