Personally my vote goes toward the Tyranids of the Warhammer 40k universe, for a good number of reasons.
They are controlled by a single consciousness that spans the entirety of their race, unsurprisingly called the 'Hivemind,' the physical manifestation of which is measured in LIGHT YEARS.
They devour every shred of organic matter on a given planet and apply thousands of years of evolution to the genetic identities of their prey. Literally, they will eat you, vomit you into the mycetic pools, and you will emerge a perfect incarnation of what you once were - utterly bound to the will of the Hivemind.
Most importantly though is what's written in their codex. It literally describes the Tyranids as the inevitable representation of death and rebirth, and it says of them that every living creature is doomed to stand against them, fight, and ultimately lose.
Dear god, they are HORRIFYING.
They are controlled by a single consciousness that spans the entirety of their race, unsurprisingly called the 'Hivemind,' the physical manifestation of which is measured in LIGHT YEARS.
They devour every shred of organic matter on a given planet and apply thousands of years of evolution to the genetic identities of their prey. Literally, they will eat you, vomit you into the mycetic pools, and you will emerge a perfect incarnation of what you once were - utterly bound to the will of the Hivemind.
Most importantly though is what's written in their codex. It literally describes the Tyranids as the inevitable representation of death and rebirth, and it says of them that every living creature is doomed to stand against them, fight, and ultimately lose.
Dear god, they are HORRIFYING.