The Other (Marvel Cinematic Universe)

The Other is the leader of the Chitauri, a race of aliens, and serves as a major antagonist in The Avengers, alongside his ally, Loki, and his master, Thanos.

The Other stays on the alien homeworld, telling Thanos that the universe will be his once he has the tesseract, and in exchange Loki gains control of Earth. The Other also warned Loki that if he failed to retrieve the Tesseract, Thanos would find him and punish him.

After the army of Chitauri was destroyed, the mid-credits scene revealed that The Other and Thanos survived, as their area was separate from the one that got blown up. The Other informed Thanos that Loki failed because the humans fought back, and weren't as defenseless as he had thought. He told Thanos that to fight them would be to "court death". At this, Thanos decided to take matters into his own hands.

The Other seems to possess super speed. He may return in Guardians of the Galaxy, an upcoming 2014 film that Thanos is stated to be appearing in. If neither is defeated at the end, it is possible that they might return in The Avengers 2, which will be released approximately in 2015.