Thanos (Marvel Cinematic Universe)

Thanos is the primary antagonist of the Marvel Cinematic Universe. He is a powerful alien warlord of pure evil who rules over a dead dimension and commands a massive army known as the Chitauri. He allied himself with Loki to invade Earth, and allied with Ronan the Accuser to destroy Xandar, both in exchange for the deliverance of two powerful Infinity gems, but they both failed to accomplish this task and had betrayed him.

He is portrayed by Josh Brolin.

The Marvel Cinematic Universe
Thanos's past is unknown at this point and how he came to power. Not even his species has been fully discovered, sans the assumption that he is an Eternal. It is known that at some point, he gained control over the deadly army of the Chitauri, and took the assassin Gamora as his daughter after killing her people. Also taken in was Nebula, a cyborg; she and Gamora had a sibling rivalry, but became attached, with Nebula saying "of all our siblings, I hated you the least", suggesting that there were many other siblings. Thanos once calls Gamora "my favorite daughter" without considering Nebula being present at the moment.

Thanos greatly desired the Infinity Stones, objects of immense power that held considerable dominance over the various forces that occupied the universe, and forged several alliances in order to locate them. According to Infinity War co-writer Stephen McFeely, he desires them so as to "re-balance the universe", but what this exactly means is unknown. He somehow obtained the Mind Stone, which could mind-control people, and put it into a spear of his own making; the other Stones, however, eluded him.

In The Avengers, Thanos appears in a post-credits scene, where the Other tells Thanos that the Tesseract, the Space Stone, is in a small world, a human world. It also informs him that Loki is ready to lead the Chitauri, and so he was given the scepter with the Mind Stone to go get the Tesseract. In a post-credits scene, Thanos is revealed to have been Loki's benefactor, having provided the Chitauri Army used by Loki in his attempted invasion of Earth. When advised by the Other that opposing the Avengers would be "to court death", as the human race was not as weak as Loki claimed, Thanos glances at the camera and flashes an evil grin.

Thanos plays a more active role in the film, where he has enlisted the help of Ronan, Korath, and his daughters, Gamora and Nebula, to retrieve the Orb (Power Stone) for him. As it turns out, Gamora is not actually Thanos's daughter, since Thanos killed Gamora's family and snatched her as an infant to train her into the perfect assassin, having abused and tormented her in the process of doing so. This causes Gamora to betray Thanos, which leads to a chain of events that leads to Gamora finding her true calling as a protector of the universe and a member of the Guardians of the Galaxy. When Ronan and Nebula are called to discuss Gamora's betrayal, Ronan kills The Other, who was speaking for Thanos. Thanos does not react to this, but is angry at Ronan for not obtaining the Orb (and for apparently alienating Gamora). He says he will destroy Xandar for Ronan if he brings him the Orb, and will "bathe the star-ways with [his] blood" if he does not.

Thanos promised Ronan that he will help Ronan destroy Xandar in exchange for Ronan's services. However, once Ronan gets a hold of the Orb, he feels he no longer needs Thanos help and also decides to betray him. Nebula also decides to betray Thanos out of jealousy over Thanos showing preference for Gamora over her. Ronan and Nebula take Korath with them. In the end, Ronan and Korath are killed by the Guardians of the Galaxy (including Gamora), Nebula escapes and becomes a renegade villain independent of Thanos, and the Guardians give the Orb to the Nova Corps for safekeeping. Drax the Destroyer, who got revenge on Ronan for killing his family, decides to turn his attention to Thanos, as the latter was the one who sent Ronan to kill Drax's family.

However, Thanos is still determined to find the six Infinity Stones and the Infinity Gauntlet so he can use them to conquer the universe.

Following Ultron's defeat at the hands of the Avengers, Thanos appears in the film's mid-credits scene. Fed up with his henchmen failing him and betraying him, he goes into a white room in an unknown location and takes the Infinity Gauntlet from it's hiding place, swearing to collect all of the six Infinity Stones himself.

Thanos is set to appear as the main antagonist, where he plans to achieve the stones and destroy the guardians and avengers for good.