Thanos is the overall main antagonist of the Marvel Cinematic Universe; serving as the overarching antagonist of The Avengers, Guardians of the Galaxy, and Avengers: Age of Ultron before appearing as both the main antagonist/villain protagonist of Avengers: Infinity War. He returns in Avengers: Endgame. His own main objective was to bring stability from the universe, as he believed its massive population would inevitably use up the universe's entire resources and condemn it. However, his methodology to succeed was warped; through using the Infinity Stones, Thanos intended to harness their power to exterminate half of life in the universe. Damion Poitier portrayed him in The Avengers, and later portrayed by Josh Brolin in Guardians of the Galaxy onwards.
Why He Is Inevitable
"You could not live with your own failure. Where did that bring you? Back to me."
His actor, Josh Brolin, is fitting.
He doesn't want power for power's sake, or to achieve something that will lead to him being honored and revered.
He wants to fix a real and horrible problem in the universe. Thanos saw firsthand on his own planet what happens when civilization recklessly exceeds its own limits.
He saw it coming and was powerless to stop it, which is why he’s convinced he must help stop it from happening again. That should be the backstory of a hero, the kind who bravely stands against the evil forces who would rather let people die than do the right thing.
His motivations are clear, understandable, and theoretically noble. Most beings would rule the galaxy if they got all six Infinity Stones, but Thanos wants to use them to fix its woes, even in his own horribly misguided way. And as we saw when he sacrificed Gamora, he does feel pain, but he will shoulder the personal cost of doing the right thing because he’s not as important as everyone else.
He is also an exceptionally intimidating individual, easily striking fear into those who are his allies even if they hold considerable abilities and powers, 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.
We see his point of view and understand that something must be done.
He grew to genuinely care for and deeply love Gamora as his child. Thanos believed in her abilities above all else and favored her above all of the other adopted children.
His menacing, spine-chilling voice provided by the talented Josh Brolin, who plays another Marvel character, Cable.
As the movie ends, we get a glimpse of Thanos looking all pensive and pondering while staring at the sunset, likely thinking about Gamora. Even though he appears to be at peace now that his plan has worked, it's a hollow triumph as he's all alone without the daughter he loved.
He also doesn't waste time monologuing to the heroes, letting others do it for him or speaks to the point.
Ever since he showed his true strength in both Infinity War and Endgame, Thanos had beaten nearly 30 heroes with his bare hands regards using the Infinity Gauntlet or not. And it really shows how much of a dangerous opponent he is.
Even when the Hulk tries to smash Thanos, he refuses all help before finally pummeling the Hulk into submission - to the point we never see Hulk in the movie thereafter. Thanos then proceeds to take out the entirety of the MCU's heroes without even losing once, something you can't say for any of the other villains in the franchise.
He is also shown to have an honorable side. While perfectly willing to manipulate others, he seems to disapprove of lies, as he never taught Gamora how to lie and was clearly disappointed that she lied on the Soul Stone.
His motivation as a villain in the MCU is an improvement over his motivation in the comics. He wiped half the universe out in the comics just to impress Death. By contrast, he wiped half the universe out in the MCU to prevent it from suffering overpopulation.
His defeat in Endgame isn't a typical villain dialogue "No!", or "How could you defeat me?", Thanos just accepts his loss by sitting down, not saying a word, and waits for his demise to come, like a true warrior.
Thanks to this, he became a meme for not just for laughs itself, but also a message.
He is one of the more quotable MCU characters, with all of his quotes being instantly memorable.
In Episode 2 of What If..., he redeemed himself thanks to T'Challa for telling him that genocide is not the answer unless it's "random".
He is extremely dangerous, bloodthirsty, sadistic and cruel, finding children that he can raise to be assassins and forcing them to watch as he murders their families.
His noble cause leads him to monstrous, indefensible acts. He invades planets who haven’t asked for help and murders its people, insisting he knows better than they do. He tears families and communities apart, leaving the “survivors” behind to live in a world of pain and loss.
His personality seemed to change in Avengers: Infinity War. He could be seen as a tyrannical sociopath in Guardians of the Galaxy, yet seemed like an anti-villain whose deeds were for a noble cause in Avengers: Infinity War.
Thanos does have favoritism towards Gamora, and doesn't care for Nebula. That is, until he later apologized that he treated her too harshly until being beheaded by Thor.
He was killed off anticlimactically by Infinite Ultron on Episode 8 of What If...?