Thanos is the bad guy of Avengers: Infinity War.
In the movie, the mad Titan Thanos believes himself to be the hero.
He eliminates half of every planet?s population to curb ecological disasters.
He tells his adopted daughter Gamora that the people of her planet are better off since his purge.
According to Uproxx, however, Thanos lied to Gamora.
In the first Guardians of the Galaxy it's revealed that Gamora is the last survivor of her planet.
That means Thanos killed half the planet's population, including Gamora's mother, for nothing.