*The post contains spoilers*
In the 17th century, a classical economist called Thomas Robert Malthus propounded that population grows exponentially, while the growth of food supply is linear. Therefore, he prophesied that at one point there will a catastrophe, a doomsday, in which many will die and the human race will be forced to return to a sustenance-level condition.
Circa 2018. In Marvel's latest outing Avengers: Infinity War, we meet a purple dude, Thanos of Titan (also known as the dark lord among his minions) mouthing the same Malthusian prophecy. Thanos (Josh Brolin) is by far the strongest villain of MCU (Marvel Cinematic Universe) and according to him, in order to maintain a balance between the ever-growing population of the universe and the limited resources that are available, half of the universe's population must be killed. Therefore, in Avengers: Infinity War, we see him set out to acquire all the six infinity stones by the help of which he can control the universe and reduce its population to half.
Despite being an MCU villain, Thanos is very egalitarian in his principles. He doesn't believe that the lives of rich people are more precious than that of poor. Therefore, he chooses to eliminate half of the universe's population in a random order.
Thanos is a supervillain and may I be bold enough to say also the superstar of Avengers: Infinity War, which has very many superheroes including Iron Man (Robert Downey Jr), Thor (Chris Hemsworth), Captain America (Chris Evans), Doctor Strange (Benedict Cumberbatch) Spider-Man (Tom Holland) and Black Panther (Chadwick Boseman). However, when it was first announced that Thanos will be the villain of the last Avengers films, Marvel fans had their concerns about his potential as a supervillain.
According to his comic book history, Thanos only wanted to wipe out half of the universe to impress a feminine version of death and fans feared that it wasn't a big enough incentive to make him a formidable villain for the series. However, the writers of Avengers: Infinity War, Christopher Markus, and Stephen Mcfeely, have managed to successfully turn Thanos into a multi-layered, dark lord with real emotions. Thanos, much like his comic book avatar also happens to be purple with a peculiarly squared chin.
Although his adopted daughter, Gamora (Zoe Saldana of Guardians of the Galaxy fame) despised him, in Avengers: Infinity War we learn that Thanos actually had affectionate feelings for her. He has been betrayed by her in past, and yet when he catches her and tries to elicit information from her about the location of soul stone, we see him reprimand her for lying to him. He tells her that he has taught her to be courageous and generous, but he has never taught her to lie. The conflicted father-daughter relationship between Thanos and Gamora humanizes Thanos to a great extent and although we know he is a supervillain planning a genocide that would have given Hitler an inferiority complex, we see that he isn't incapable of love. We see that he is capable of repentance and guilt.
Despite fighting all the Avengers single-handedly, he doesn't take his battles personally. He is a man on a mission and he knows that he has to fight the Avengers to accomplish it. But, he shows respect to his enemies when it is due. At a critical point in the film, he stabs one of the Avengers as he sees the Avenger on the verge of dying, he almost apologetically says that he had no option but to stab him.
As the dark lord with an army of followers, Thanos could have very well sat on his throne and given orders and expected his underlings to carry them out. In fact, he did tell Loki and Ronan (in previous films) to bring him the infinity stones. However, when they failed he took the task onto himself. "Fine, I'll do it myself," he said. In Avengers: Infinity Wars we meet Thanos as a hands-on villain. Most of his fights, Thanos fights himself and he does so very intelligently.
Despite being called an Avengers film, in Avengers: Infinity War we do not see all the Avengers reunite at any point. The only uniting factor for all the Avengers in this film is Thanos, a hyper-intelligent supervillain that they will have to defeat in order to save the universe.
The apocalyptic film ends on a somber note. It tells you loud and clear, that the Marvel universe will explode and collapse soon. In the end, as Thanos sits brooding and melancholic staring at a distance, a chill runs down your spine because you know that the worst of his wrath is yet to come. He is by far the best villain in MCU.