Avengers: Infinity War and Avengers: Endgame are two epic Marvel Cinematic Movies loosely based on the events of the comic book series: "Infinity Gauntlet". Besides Thanos himself, one of our main protagonists came in the form of Adam Warlock, an otherworldly figure who appeared in an early issue of the Fantastic Four, created by Stan Lee and Jack Kirby. While Warlock himself does not make an appearance in Endgame, his future is almost assured in the MCU due to his reference in the post credit scene of James Gunn's Guardians of the Galaxy Volume 2.
First hitting the scene as the strange character simply called "Him", Warlock was created by a group of scientists dubbed the "Enclave" who were attempting to create the ultimate form of man (as is mad scientists' want). Realizing that the earth held little for him after a short misunderstanding with Reed Richards and his family, Warlock headed for the stars looking to uncover the mysteries of the cosmos and his own life. From here, Adam Warlock continued to be fleshed out under the pens of Roy Thomas and Jim Starlin, appearing in numerous cosmic Marvel stories and butting heads with both Thanos and other space based villains.
In the storyline Infinity Gauntlet, Warlock rallied together with the Marvel heroes of Earth, attempting a suicide mission aimed at stopping Thanos from continuing to use the power of the Gauntlet. Sacrificing the lives of the heroes themselves by hurling them at Thanos, Warlock hedged his bets on the Silver Surfer, now acquired by the MCU due to the Disney acquisition of Fox Studios, being able to grab Thanos' gauntlet from his hand. Due to a split second mistake, this route was unsuccessful and Warlock created an additional plan using both the deities of the Marvel Universe and Thanos' daughter Nebula to grasp the gauntlet for himself and undue Thanos' destruction.
While Adam Warlock has not been cast as of yet for any upcoming Marvel Cinematic Universe appearances, his eventual landing in the slate of films is most assured thanks to the clues laid at the end of Guardians Volume 2. If push came to shove, he'll most likely appear in Gunn's Guardians of the Galaxy Volume 3 but since that is years away, don't expect Adam to be popping his head up, Thanos or no.
You can find the description for Avengers: Endgame below:
"After the devastating evens of Avengers: Infinity War (2018), the universe is in ruins due to the efforts of the Mad Titan, Thanos. With the help of remaining allies, the Avengers must assemble once more in order to undo THanos' actions and restore order to the universe once and for all, no matter what consequences may be in store."
Avengers: Endgame is in theaters now.