From the Alien Division: XENOMORPH from "Alien" (1979) vs THE THING from "The Thing" (1982)
The deadliest Alien creature of all time versus the shape-shifting unknowable abomination. Who will reign supreme?
XENOMORPH: Uncertain in their original, the Xenomorphs need a host body to infest before bursting out of the chest cavity. Acid for blood, razor-sharp claws and tails, rows of teeth and a secondary mouth, the Xenomorphs kill and infect while working together. Weaknesses: Few, although they are susceptible to death by fire and explosions and have no supernatural powers.
THE THING: An unknown organism from outer space with the ability to assimilate and take on the forms of other creatures, human and non-human. The host organism can survive on the cellular level in extreme cold and kills a host before taking over its likeness. Weaknesses: Extremely few. Dislikes fire.
UPDATE: WINNER, by a VERY close margin, THE THING!