Adam Warlock has always been a pain in the side of Thanos, the Mad Titan. The cosmic hero has helped foil Marvel's greatest villain's plans on numerous occasions, including the time he sacrificed himself to turn Thanos in stone.
Adam Warlock first debuted in the pages of Fantastic Four, as he was created to be the perfect human by a group of evil scientists known as the Enclave. Eventually, Warlock obtains the Soul Gem, which grants him immense powers. Before Thanos would wield the Infinity Gauntlet, he sought out the Infinity Stones to power a device that would turn the sun nova. In an effort to stop him, Warlock (and a handful of other cosmic heroes) are killed and their beings are transferred inside the Soul Gem.
Marvel Two-In-One Annual #2 by Jim Starlin, Joe Rubinstein, Petra Goldberg, and Annette Kawecki, opens with Spider-Man's dreams of the Avengers being defeated in space by Thanos. Once he wakes up, Spidey teams-up with the Thing and the two fly into space to check out what's really going on, and once they arrive, they are attacked by monsters. Meanwhile, it's revealed Warlock is living in paradise in the soul gem with his fellow fallen heroes. However, he decides he needs to do something about Thanos. Once the heroes seem defeated by Thanos, Spider-Man steals the Soul Gem from Thanos' device and frees Warlock's soul, who promptly turns the villain into stone with a blinding light.
Warlock manages to save the heroes, but his soul is transferred back into the Soul Gem. The heroes grieve the loss of Warlock, as they hold a funeral with his tombstone reading "... here lies Adam Warlock. God slayer of two worlds, and tormented soul." Captain Marvel says he can only wish to "pass as honorable as he." Warlock is later seen inside the Soul Gem paradise with Gamora and Pip the Troll, where he says he's happy to make Thanos finally pay for his crimes.
While Thanos' most sinister plans involving the Infinity Gauntlet were still to come, Warlock proved in one of his earliest encounters with Thanos that he was a formidable opponent. He turned Thanos into stone and in the process, saved numerous Avengers and who knows how many human lives. Marvel's greatest heroes would have been in big trouble if Warlock didn't show up and save the day. When it comes to taking down Thanos, Adam Warlock is about as valuable of an asset as any superteam can have - this issue certainly proved that.