Death
At the end of the first “Avengers,” Thanos smiles when he’s told that to face Earth’s Mightiest Heroes is “to court Death.” This is because in the comics, Thanos is in love with Death (also called Lady Death) and his motivation for The Snap is to try and impress her by wiping out half of all life. It’s a shame that Lady Death, the Marvel grim reaper, got cut from Thanos’ story, as she kind of makes more sense than Thanos’ nonsensical plan about resource scarcity.