Thanos’ motivations in Anthony and Joe Russo’s highly-anticipated 2018 superhero film, Avengers: Infinity War, are described as being psychotic and compelling.
The supervillain’s motivations for obtaining the Infinity Stones, aside from becoming all-powerful, remain unknown.
Of course, since Death isn’t a part of the MCU yet, Thanos might have other reasons for gathering the Infinity Stones and affixing them to the Infinity Gauntlet.
Although he’s been absent for the past few years, his seemingly unyielding mission remains the same: gather all six Infinity Stones and affix them to the Infinity Gauntlet.