The Russo Brothers Talks About Thanos' Backstory And His Powers In AVENGERS: INFINITY WAR
Joe and Anthony have actually explained the villain's origin story during a recent interview and told us pretty much everything we need to know about what motivates him.
"Thanos is this virtually indestructible character who’s stronger than the Hulk, and has invincible skin. He’s from a planet called Titan. Many years prior to the film his planet was experiencing a cataclysmic shift. They were running out of resources, and they were overpopulated. Thanos made a recommendation that they exterminate half the population randomly in order to save the rest of the population. Of course, the Titans rejected his notion, branded him a mad man, exiled him, and the planet ended up dying. So he has taken it upon himself to go planet-by-planet throughout the universe and wipe out half of the population of each planet as a way to correct the planet and bring it back into balance."
The filmmakers then went on to elaborate on what he has planned for Earth's Mightiest Heroes (and the wider universe as a whole) and it's fair to say Captain America and company should be worried.
"Once he hears about the stones, he realises that if he can get hold of all of the Infinity Stones he can control the entire universe. With the snap of his fingers he could correct the universe permanently by removing 50 per cent of life from it. So, these are incredible stakes for our characters. If the Avengers were built for anything, it’s stopping Thanos from completing his goal."