Throughout The Infinity Gauntlet, Thanos tormented his granddaughter Nebula (in the MCU, she's his adoptive daughter), keeping her imprisoned in a sort of living death. With the Mad Titan's body unconscious and unprotected while his astral form combats Eternity, Nebula seizes the opportunity to remove the Infinity Gauntlet from his hand and become omnipotent herself. But before she can exact revenge upon Thanos, he's teleported to safety by Doctor Strange, and convinced by Adam Warlock to help them stop his granddaughter.
The Mad Titan manipulates Nebula into turning back the clock 24 hours, which leaves her in possession of the Infinity Gauntlet but resurrects all of those who died with the finger snap, and in the ensuing battle, leaving most of them with no memory of what took place. Nebula then defeats Doctor Strange, Thanos and the returning cosmic entities, but Warlock transports himself and the Silver Surfer to Soul World, where he exploits his link to the Soul Stone to generate "disharmony" among the other five, causing unbearable pain for Nebula, who's forced to cast off the Gauntlet. A free-for-all ensues for control of the Infinity Gauntlet, only for Adam Warlock to reappear and claim it, assuring he will be "a god who can be trusted."
Choosing death over imprisonment, Thanos activates a thermonuclear device on his belt, and is cast into space by Thor, where he seemingly dies. However, like the other casualties of The Infinity Gauntlet, the Mad Titan isn't really dead, either. Instead, accompanied by Gamora and Pip the Troll, Adam Warlock travels 60 days into the future, to an "unnamed planet," where he finds Thanos, living a solitary life as a simple farmer.
None of that's to suggest Adam Warlock will suddenly appear in Avengers 4 to save the day -- he likely won't be fully introduced until Guardians of the Galaxy Vol. 3 -- or that Josh Brolin's Thanos will close out his MCU arc raising grain on a distant world. No, Brie Larson's Captain Marvel will likely be the cavalry that helps turn the tide against the Mad Titan, but it's easy to imagine Karen Gillan's Nebula as central to the defeat of her father, and to righting his wrongs, which includes the death of her adoptive sister Gamora (Zoe Saldana). The question, however, is what other sacrifices will have to be made. With several of the stars of the MCU reaching the end of their contracts, we're bound to witness some heroic deaths that not even the power of the Infinity Gauntlet can undo.
Directed by Joe and Anthony Russo, Avengers: Infinity War stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Paul Bettany, Anthony Mackie, Paul Rudd, Elizabeth Olsen, Tom Holland, Benedict Cumberbatch, Chadwick Boseman, Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Tom Hiddleston and Josh Brolin.