You think you know pain, Asgardian? He will make you long for as sweet as pain!
~ The Other describes Thanos' wrath.
The Tesseract has awakened. It is on a little world, a human world. They would wield its power, but our ally knows its workings as they never will. He is ready to lead, and our force, our Chitauri, will follow. The world will be his, the universe will be yours. And the humans, what can they do, but burn?
~ The Other to Thanos.
The Other is a major antagonist of the Marvel Cinematic Universe. He is the leader of the Chitauri and emissary of Thanos. He first appeared as the secondary antagonist of The Avengers and later as a minor antagonist in Guardians of the Galaxy.
The Other stays on the alien home world, 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 give Thanos 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.
Guardians of the Galaxy (2014)
In Guardians of the Galaxy, The Other called Ronan and Nebula over to Thanos's domain when Gamora betrayed them and the Orb was kept from them. Ronan argued with The Other, and raised his voice, to which The Other yelled at Ronan to lower his tone in front of Thanos. In response, Ronan used the power of his hammer to twist The Other's head 180 degrees, snapping his neck and killing him. Thanos took little notice of this, and starts speaking for himself.
Powers and Abilities
The Other seems to possess super speed, which he demonstrates to run over to Loki at one point in response to him reminding him that they do not yet have the Tesseract. He also teleports Loki to the Earth at one point. Not much of his power has been seen, however, as he is not seen in action as much and is original to the film series.
The Other speaking to Loki.
The Other kneels before Thanos' Throne.
The Other bowing to Thanos.
Ronan looking at The Other as his neck is snapped by the Universal Weapon.
In the comics, "The Other" was an alias of Chthon the Elder God. However, his appearance closely resembles that of Thanos' second-in-command, Corvus Glaive, also being very similar to Herr Kleiser from the Ultimate Marvel Comics series.
He looks similar to the Flash Gordon villain Klytus.
There are rumors that Thanos will revive The Other, though it is unknown whether Thanos has the power to do so. However, it is now possible for Thanos to have the power to resurrect the Other as he now has the Soul Stone, which grants him dominion over souls and the divine right to decide who lives who dies. However, in Avengers: Endgame, it's revealed that Thanos destroyed all the Infinity Stones after causing the Snap and retired from his warlord role, which likely means that he didn't resurrect The Other as he will have now no longer a purpose, as his purpose was to serve Thanos.
According to James Gunn, The Other was killed so that Ronan the Accuser, the main antagonist of Guardians of the Galaxy, would not look weak compared to Thanos.