The so-called Alien in the Alien movies. In some references it is more specifically designated as "Xenomorph XX121".
Taxonomy name: Linguafoeda Acheronsis ("foul tongue from Acheron") or Internecivus raptus ("murderous thief").
This highly agressive and lethal alien monster was designed by Swiss surrealist artist Hans Rudolf "Ruedi" Giger in the late 70s.
Nobody here but us chickens!