Thanos

"I shall honor our agreement, Kree, if you bring me the Orb. But return to me again empty handed and I will bathe the starways in your blood."

- Thanos to Ronan the Accuser

Thanos, also known as the Dark Lord by his most loyal underlings and the Mad Titan by the galactic communities, is a powerful, cosmic warlord who rules over a distant region of space and also commands a massive army known as the Chitauri. His own main objective is to obtain the Infinity Stones, and his desire to achieve this goal is what led him to forging deals with the villains Loki and Ronan the Accuser in their respective campaigns against Earth and Xandar. Both of these new alliances cost Thanos much of his resources, including one of the stones and the loyalty of his two daughters, Gamora and Nebula, and also inadvertently resulted in the formation of the two superhero groups the Avengers and the Guardians of the Galaxy. Eventually, he lost his patience with his servants and opted to seek out the Stones personally.

Training his Daughters
"Flesh is weak. Weakness must be cast aside for the sake of power."

- Thanos

Thanos became one of the most powerful and feared warlords ruling over a distinct region of space, having gained control over the deadly army of the Chitauri, eliminated the Zehoberei race and a Luphomoid family to raise two young women from both races, Gamora and Nebula, to be devoted and deadly assassins. Usually when Nebula lost in a duel against Gamora, Thanos removed a body part from her. 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. He successfully located at least one of the stones; the Mind Stone, hiding it inside a Scepter that was capable of manipulating minds.

Through many years of searching, Thanos discovered a lead on the Orb's location, sending Nebula and Gamora to the Cloud Tombs of Praxius under the command of his ally, the Kree soldier Korath the Pursuer. Nebula fell victim to a trap during the mission, and Thanos, not one to tolerate failure, forbade Gamora from rescuing her. Nebula was forced to amputate her own arm in order to escape. The Orb was never recovered, but Thanos let the failure pass and resumed his search.

Aiding Loki
"You will have your war, Asgardian. If you fail, if the Tesseract is kept from us, there will be no realm, no barren moon, no crevice where he can't find you. You think you know pain? He will make you long for something as sweet as pain."

- The Other to Loki

Thanos discovered that the Tesseract was on Earth and allied himself with Loki in order to retrieve it, providing him the Scepter and his Chitauri army, who would help him conquer the planet in exchange for the Tesseract. Through his intermediary, The Other, Thanos threatened the Asgardian god of mischief, saying that if he failed in delivering the Tesseract, Thanos would force him to endure a new kind of suffering. Despite his vast army of the Chituari and powerful weapons, Loki was quickly defeated and scepter-laden Infinity Stone ended up in HYDRA's hands while the Tesseract transported to Asgard by Thor, along with the now captured Loki. The Other reported to his master, who has his back turned, that the Earth's inhabitants were not as weak as they were thought to be. He also declared that challenging the Earth's heroes would be to court Death. To this, Thanos rose to his feet, turned around and simply smiled at the prospect.

Quest for the Orb
"The Orb is in my possession, as I promised." "Bring it to me." "Yes, that was our agreement."

- Ronan the Accuser and Thanos

Some time later, Thanos brokered a deal with his old ally, Ronan the Accuser of the Kree Empire, promising to lend a fraction of his forces in a genocide against the Xandarians in exchange for locating the Orb for the Mad Titan. Ronan and Korath the Pursuer quickly discovered the true location of the Orb on Morag and attempted to deliver it to Thanos, but an unexpected turn of events meant the stone fell into the possession of Ravager member, Star-Lord. Unwilling to be denied the stone, Thanos ordered Ronan to pursue Quill and recover the stone, sending Gamora to aid the Kree in his pursuit. Gamora found Quill first, cornering him on Xandar where he was attempting to sell the Orb. She recovered it, but what Thanos did not realize is that Gamora had chosen to cut all ties with him and now planned on handing the Orb over to another party, suspected to be the infamous Collector, who also sought the stones. When Ronan relayed news of Gamora's betrayal to Thanos which he had learned had been planned for some time, the Kree berated the Mad Titan for not taking the situation seriously and even murdered The Other when he lectured Ronan on not showing Thanos respect. Undaunted by The Other's death and Ronan's complaints, Thanos turned Ronan away, instructing him to return to his task and correct Gamora's betrayal, which he was only slightly irked by. He instructed Nebula to take Gamora's place as Ronan's aide.

Betrayed by Ronan the Accuser
"Thanos is the most powerful being in the universe!" "Not anymore."

- Korath the Pursuer and Ronan the Accuser

As Ronan the Accuser and Nebula both eventually stole the Orb from Gamora, Star-Lord, and their allies, but when Thanos was contacted by Ronan to be updated on their progress, he was furious to discover that the Kree, having experienced the true power of the Orb, intended on keeping the Infinity Stone for himself, despite Korath the Pursuer expressing his fear of Thanos being the most powerful being in the universe. Nebula joined with Ronan, contemptuous towards Thanos after the horror he forced her to endure throughout her youth. Now believing himself superior to Thanos, Ronan promised to come after the Dark Lord when Xandar was destroyed. Unphased, Thanos cut contact with them without a word. Ronan would eventually perish at the hands of the Guardians of the Galaxy, who gave the Orb to the Nova Corps, making another Infinity Stone lost to Thanos.

Coming Out to the Open
"Fine. I'll do it myself."

- Thanos

With both Loki and Ronan the Accuser having failed Thanos in their tasks of conquering worlds and bringing him the Infinity Stones, and both of his daughters lost to him, Thanos had finally grown tired with the lack of progress in his crusade and decided to take matters into his own hands. Thanos retrieved an Infinity Gauntlet and began to hunt for the Infinity Stones himself, believing himself to be capable of completing the task, smiling confidently to himself at the prospect of victory.

Personality
Thanos is nothing more than the ultimate personification of power hunger, sadism, cruelty, megalomania, infinite destruction, death, power and madness. Searching for the Infinity Stones with the apparent goal of controlling all of existence. He desired to use the Tesseract to look beyond the known worlds to find greater ones that it would unveil. He is also relentless by finding children that he can raise to be assassins and forcing them to watch as he murders their families, with Ronan the Accuser showing visible signs of fear in his presence and Loki doing so at the mere mention of him, as well as being able to command the Chitauri army unchallenged.

He has an unforgiving nature; The Other warned Loki that he would know a new kind of pain if he did not give them the Tesseract, Thanos threatened to bathe the starways in Ronan's blood if he failed to deliver the Orb and forbade Gamora from rescuing Nebula when the latter fell into a trap whilst on a mission in the Cloud Tombs of Praxius. He has little to no regard for his followers, showing absolutely no empathy when Ronan killed The Other and referring to Gamora as his "favorite daughter", even with Nebula present.

He inspires no love, as he is despised by his own "daughters", Gamora and Nebula. Raising them in a brutal way Thanos would pit them against each other in the hope that Nebula would beat Gamora, however when Nebula lost he would remove parts of her in order to make her stronger taking her apart piece by piece and replacing her with artificial limbs and organs so she would be able to defeat her sister. He is also manipulative and mistrustful, sending Ronan to retrieve the Orb for him and not telling him that it contained an Infinity Stone. He keeps a low profile, lurking in the shadows and making others do his work for him. However, after both of his alliances backfired, he decided to hunt for the Infinity Stones himself.

He is also highly confident, to the point of borderline arrogance, as he was shown to be smiling when The Other told him challenging the Avengers is like courting Death. He also smiled confidently after deciding to hunt for the Infinity Stones himself.

Powers and Abilities
""Master, you cannot! Thanos is the most powerful being in the universe!""

- Korath to Ronan during Ronan's betrayal

Thanos has not yet demonstrated any of his powers at this point. However, it is conceivable that he is extremely powerful, able to strike fear into an Asgardian like Loki and a Kree like Ronan the Accuser, and command the Chitauri army unchallenged. When Ronan the Accuser was about to betray Thanos and use the Orb for himself, his servant, Korath fearfully stated that Thanos is the most powerful being in the universe. Ronan, however, ignored Korath's advice and was confident that he could kill Thanos with the power of the Orb. Nevertheless, Thanos displayed no signs of concern after Ronan threatened him. When Nebula told Gamora of her plans to kill Thanos, she plainly told her that she doesn't know if that's possible.
 * Master Manipulator: Without leaving his throne, Thanos ultimately caused both the Chitauri Invasion and the Battle of Xandar.

Allies

 * Loki
 * The Other † - Subordinate
 * Chitauri - Subordinates
 * Leviathans - Subordinates

Enemies

 * Gamora's Father † - Victim
 * Gamora's Mother † - Victim
 * Avengers
 * Captain America
 * Iron Man
 * Hulk
 * Thor
 * Black Widow
 * Hawkeye
 * Guardians of the Galaxy
 * Star-Lord
 * Gamora - Adopted Daughter
 * Drax the Destroyer
 * Rocket Raccoon
 * Groot
 * Nebula - Adopted Daughter
 * Ronan the Accuser † - Former Subordinate
 * Korath the Pursuer † - Former Subordinate
 * Nova Corps
 * Collector

Trivia

 * In the comics, Thanos was a member of the Eternals, a race of superpowered beings that descended from a caste of humans genetically enhanced by the Celestials. Thanos himself was the son of Mentor, the leader of an Eternal colony on Saturn's moon of Titan. Much of Thanos' villainous motivations in the comics revolve around his romantic feelings for the entity Death. In the famous Infinity Gauntlet storyline, he became the master of the Infinity Gauntlet, which he used to murder most of the universe's inhabitants in an attempt to impress Death. He is one of the Avengers' most historical foes, but when he took a break from being a conqueror, Thanos was entrusted with the Reality Gem of the Infinity Gems.
 * The name "Thanos" is based on the name of the mythological Greek figure, meaning "death".
 * During the Skirmish on Knowhere, Nebula states that out of all of their siblings, she hated Gamora the least. This suggests that Thanos has other "children."

Behind the Scenes

 * Thanos' presence in The Avengers was kept top secret until the release of the movie.
 * Damion Poitier was credited as "Man 1" despite actually playing Thanos.
 * Josh Brolin was uncredited for his appearances in Guardians of the Galaxy and Avengers: Age of Ultron.
 * Along with Bruce Banner, James Rhodes, Howard Stark and Fandral, Thanos is one of the few characters in the Marvel Cinematic Universe played by different actors in different movies.
 * It was Joss Whedon's idea to reveal Thanos as the true villain of The Avengers, but ironically he considered the villain too difficult to write.
 * Thanos was the main villain in Nicole Perlman's draft of Guardians of the Galaxy: Whedon asked Thanos's role be downsized and Gunn agreed.
 * Joss Whedon assisted James Gunn with the casting of Thanos.
 * Josh Brolin took inspiration from 's performance as in  in his portrayal of Thanos.