The Predator

A Predator ship crash-lands on Earth. Army Ranger sniper Quinn McKenna and his team are attacked by the Predator on a hostage retrieval mission. McKenna incapacitates the Predator and has its armor mailed off to prove the existence of extraterrestrial life. At the behest of government agent Will Traeger, he is captured and held for examination. Traeger also takes the Predator to a lab for experimentation and observation, recruiting evolutionary biologist Casey Bracket to study it. The Predator awakes, breaks out of its bonds, kills lab workers, but spares Bracket before leaving. Read more on Wikipedia.