Following Avengers: Infinity War, many fans of the MCU have taken a stand in support of Thanos, the strongest "villain" in the universe to date. Thanos is hell-bent on achieving balance in the universe, and the only way he believes this is possible is to eradicate half of the universe's population in order to prevent the complete exhaustion of resources and bringing an end to life.
Thanos is not a typical villain; he doesn't seek to control the universe or to destroy it, he seeks only to save it from a seemingly inevitable fate. This has made Thanos such as a relatable that #Thanosdidnothingwrong has become a trending social tag since Infinity War released.
With so many people behind Thanos' motivations and methods, we have to ask ourselves whether Thanos is actually a villain, or if he is a hero on the wrong side of the story. The difference between the two in any tale is a matter of perspective.
A Tragic Hero
Similar to Captain America, examining the character arc of Thanos puts him under the category of tragic hero (since it is to be presumed that Thanos will lose and die by the hand of the Avengers in the next film). Even more similar to Captain America is Thanos' dedication to the idea of sacrifice, which will become his downfall when the Avengers seek to (surprise) avenge and restore the deaths of half the universe's population. Excessive pride and disrespect for the natural order of the world are two important traits of a tragic hero that Thanos exhibits. Perhaps the most interesting element, however, is the idea of "nemesis."
Nemesis is a classic idea a hero character like Thanos must always face a punishment that they cannot avoid as a direct result of their character flaw. The greatest sacrifice Thanos has made is that of his daughter, Gamora. Thanos had a genuine love for his daughter, so much so that he was brought to tears when he realized he had to give her life for the Soul Stone. These qualities and developments put Thanos alongside classic characters like Oedipus, Jay Gatsby, and Anakin Skywalker who are all heroes plagued by a severe character flaw.
Thanos' motivations are what separates him from other binary good/evil villains. Thanos has actually experienced the effects of inaction in his own homeworld. Titan, his home planet, was destroyed after his proposal to randomly kill half of the world's population was rejected.
This experience leads Thanos to believe that he is the only one in the universe who can maintain balance, and he might be right. It is an unfortunate truth that resources are finite, and while defending Earth is a noble cause, heroes are not addressing big-picture issues for humanity (at least that we've seen, Stark and Wakanda technology could have big impacts on these problems).
In an ever-growing universe, how does life sustain itself? While the Avengers are thinking about the short-term safety of the world, Thanos is trying to achieve long-term prosperity.
Thanos the Hero
In his own story, Thanos is a hero who has endured countless trials to obtain the Infinity Stones in order to save the universe from its doom. Characters like Iron Man and Captain America are notoriously closed off to opposing ideologies. This means that, unfortunately, Thanos becomes a villain in the Avengers' story because his ideals do not coincide with the heroes of Earth.
While we may never see the impact of population in the MCU, the issue of sustainability is still omnipresent. Without a hero like Thanos, who has the resolve to make hard decisions (unlike any of the Avengers), the entire universe could eventually collapse.