Thanos, or as he is referred mostly, The Mad Titan Thanos is going to be the big baddie for the next two films, Avengers Infinity War part 1 and 2. The character first made his debut in Iron Man issue 55 and has been one of the best villains of the universe. The character belongs to a race known as the Eternals, this race was created by the Celestials.
Born on Saturn’s moon, Titan Thanos amongst the Eternals was different, having a different gene in him and being a Deviant. Which is something like mutants on earth? Deviants were way more powerful than the normal Eternals but were different looking.
Because of the discrimination that he faced because of how he looked, Thanos realized that he, the young prince will always be different. He since his childhood became jealous of his brother, Eros. Eros is later an Avenger by the name Starfox.
Thanos in his growing years became fascinated with destruction and death. His interest became an obsession when he reached the temple of Death, where he finds his eternal love, Mistress Death. Mistress Death was not a single bit interested in the Mad Titan and just to woo her, he decided that he will eradicate all life from the universe.
Later when his father comes to know of Thanos’ plans, he orders him to leave the planet, after which Thanos travels around in the space gathering knowledge and coming across various alien races.
Amongst these alien races, he takes the warriors into his own army and also adopts two girls who he thinks to be much better than the rest. These two are Nebula and Gamora. Due to being this long in space he is also able to absorb cosmic rays, this is possible because of his mutation. And hence he becomes the most powerful titan.
After this, he attacks his home planet and even kills members of his own family. His father and brother survive as at that time they’re not on the planet. This resulted in him becoming the king of Titan and hence being called the Mad Titan.
After this, he created a space sanctuary and started his quest for the Infinity Gems, for his Infinity Gauntlet. The term ‘Infinity Gem’ too was given by him. So this was all about Thanos, who haven’t have had his hands on any of the Infinity Gems. This is why Avengers: Infinity War is in two parts.