Calvin

Calvin is the name given to the Martian alien and main antagonist of the 2017 movie "Life". This species is believed to have wiped out all life on Mars, therefore making it an apex predator.

Each cell belonging to Calvin is a muscle, a nerve and an eye at the same time. It is semi-intelligent.

Calvin was presumed to be a species whom lived on mars and dominated the Martian soil, In a "hibernation" state the crew wake Calvin up, it's first priority is clearly to grow, second... ravage the crew.

History
Calvin attacks Hugh's hand while he is testing Calvin in the lab. Calvin breaks Hughs hand and then uses a needle to escape from the container. Calvin then enters a container where a lab rat is being kept and consumes the rat and grows slightly larger. Upon seeing this, Rory runs into the lab and rescues Hugh however in the cost that he becomes stuck in the lab with Calvin as David locks him in. Rory unsuccessfully tries to kill Calvin with a flamethrower and Calvin enters his mouth and devours his insides before emerging bigger again. The flamethrower then causes the air vents to open and Calvin is able to escape into the ship.

Calvin is next seen when it grabs onto Ekaterina, the captain, while she is in space trying to fix a vent. Calvin causes her suite to break causing water to flow into her helmet, drowning her. However she was able to prevent David from opening the door letting Calvin back in. However despite this Calvin makes his way into one of the thrusters.

Calvin then attaches itself to Hugh's leg which he doesn't feel because of his disability and feeds on him. The loss of blood kills Hugh and after the crew discover Calvin it proceeds to chase them.

Another ship then arrives and attempts to knock the international space station (the crew are in) into space to prevent Calvin getting to Earth, however Sho mistakes the ship for a rescue ship and tries to get to it. After a struggle with Calvin Sho prevents Calvin from getting onto Miranda. Calvin kills the crew of the fail safe ship and Sho is dragged into outer space.

The last two survives of the crew David and Miranda come up with a plan to lure Calvin in David's pod so that David will sacrifice himself to take Calvin into outer space and prevent it from reaching Earth, while Miranda will go back to Earth. However Miranda's pod hits a bit of space debris causing her to fly into outer space and Calvin prevents David from controlling his pod by grabbing onto his arms causing David's pod to fly onto Earth, reentering the atmosphere and landing in Vietnam. We are left with a cliff-hangar as the credits role in just after some unknowing fishermen open the shuttle-hatch, revealing Calvin still alive and holding David inside, slowly feeding on him. Our only two assumptions are that Calvin was killed later by military forces or wiped out all life on Earth.