With Avengers: Endgame fast approaching, we are finally going to see how the Avengers manage to find a way to stop Thanos and the staggering power of the Infinity Gauntlet, which was just used to kill off half of the universe. The sheer magnitude of the Infinity Gauntlet's destructive abilities has caused many fans to be fascinated with the cosmic device.
At the same time, though, the very nature of creating a weapon that is "the most powerful" has led to the obvious question of, "Okay, but is there seriously nothing else more powerful than it?" The truth of the matter is that there appears to be one other cosmic item within the Marvel Multiverse that is considered more powerful than even the Infinity Gauntlet. Its existence, however, is a matter of controversy in and of itself.
While he has done many famous comic book stories over the years, it is clear that Jim Starlin is now best known for being the writer behind the Infinity Gauntlet, the 1991 crossover where Thanos put together the aforementioned collection of the Infinity Stones (then known as the Infinity Gems) to wipe out half of the universe.
Since then, Starlin has done a number of follow-up stories that feature both Thanos and Thanos' heroic counterpart, Adam Warlock. His first two follow-ups, Infinity War and Infinity Crusade, directly followed Infinity Gauntlet in 1992 and 1993, respectively. Starlin then took a decade-long gap before returning to Marvel in 2003 with Marvel: The End.
The End was a series of titles that Marvel released between 2003 and 2010 that purported to show the "final" story featuring Marvel's various heroes. However, Starlin took it a step further with his six-issue series titled simply Marvel: The End (written and drawn by Starlin and Al Milrom). The concept of the series is that the supreme being in the Marvel Multiverse decided that there were too many superhero resurrections. It was tipping the universe out of balance, as there were more people alive than should be alive. So a powerful weapon called the Heart of the Universe was created to help balance things out.
An Egyptian pharaoh by the name of Akhenaten was given the weapon and Akhenaten proceeded to wipe out most of the heroes in the Marvel Universe. However, the remaining heroes, along with Doctor Doom (who wanted the weapon for himself) contested Akhenaten and in the end, the weapon found itself in the hands of Thanos.
This was not something that the remaining heroes (and the cosmic beings of the Marvel Universe) were cool with happening...