Thanos's motivation in "Infinity War '', and "A Valediction: Forbidding Mourning" by John Donne.

Thanos is one of the best MCU villains to be captured on the screen.  To some the greatest. In fact, due to building his character since  "The Avengers", and familiarizing the audience with his persona, it is going to be quite challenging to yet repeat and create an even better villain like "Kang: The Conqueror" is supposed to be. But what really makes Thanos such an incredible villain and character in the world of MCU?

Villains in MCU, but generally in Comics films are often undervalued and their only motivation is to destroy the world like "Malekith" in "Thor: The Dark World". They are usually not pre-build and developed enough during the film so we consider them simply as good characters.

Moving on to Thanos, his pre-development started after "The Avengers” in 2012, when for the first time audiences were able to see him sitting on his throne. After such a disastrous fight in New York and alien threats with such a vast army, he was then considered dangerous. He had some cameos at the end of "Guardians of the Galaxy '' and "Avengers: Age of Ultron '' that reminded the audience that there is a big threat somewhere waiting for an opportunity to strike.

It wasn't until "Avengers: Infinity War '' that Thanos made his debut as the actual villain in the story. Also then he enters the screen as a very experienced character and kicks Hulk's ass, killing 50% of Asgardian people.

Here comes his plan for the universe - To erase 50% of living things from the universe, meaning 50% of the human population down from Earth. We already get some important information about his abilities from the first scene - He is powerful, he is smart, and he has some iconic lines too, but he as well remembers Loki, whom he kills.

We are as well presented with his past and meeting Gamora - his "Daughter" he calls her.  There is said one of the lines that indicate similarity with John Donne's poem, "Perfectly balanced as all things should be ''. There is a place for tragic but also great things. Wars, slavery but also freedom and progress. If properly balanced, create harmony in the universe.

In John Donne's poem "A Valediction: Forbidding Mourning", there is a metaphor of a compass that can work only if balanced correctly. In that case, if love is balanced between spiritual and physical, only then is able to survive separation. Thanos's love for Gamora is balanced in a way. He loves her, but he also needs to sacrifice her in order to bring balance to the universe.

To sum up, Thanos is such a well-written and important character in the MCU and also in the history of cinema. There are some similarities with the poem of John Donne,  but it is rather unlikely that his motivation was inspired by XVII-century love poetry.