The Living Tribunal is the most powerful creature in the Marvel Universe, the supreme judge of all reality, but readers are probably unaware that the one responsible for the creation of its current iteration is none other than Thanos, the Mad Titan.
The Tribunal first appeared in a Doctor Strange story, "The End of the Ancient One!" in Strange Tales #157, by Stan Lee and Marie Severin. The function of this cosmic entity is to safeguard the Multiverse from anything threatening to upset the cosmic balance. The One-Above-All (Marvel's equivalent to God), created him to fulfill this purpose, and as such the Tribunal is considered nearly omnipotent. For example, his "judgment" can nullify even the power of the combined Infinity Stones. This is possible because, contrary to other cosmic beings, the Living Tribunal does not have a counterpart in each universe, there is only one in the whole Multiverse.
After his first sporadic appearances, the Living Tribunal established his role as the supreme being in the universe in the aftermath of the Infinity Gauntlet saga. After Adam Warlock acquires the Gauntlet, his right to absolute power is contested by the assembled cosmic beings, including Eternity, the embodiment of reality, who feels usurped. The Tribunal presides over the trial and rules that Warlock is unfit to possess the power of the Gauntlet, which leads to the distribution of the Stones (then known as Infinity Gems) among the of the Infinity Watch. For the occasion, the Tribunal even borrows a famous Spider-Man line, saying, "With great power comes great responsibility and little happiness." The Living Tribunal and Adam Warlock's paths, however, would cross again in an unexpected way.
In Infinity Finale - by Jim Starlin, Ron Lim, Andy Smith, and Guru-eFX - takes the place of the Living Tribunal, who has been previously slain by the Beyonders during the Secret Wars event. This is possible only because when alternate Warlock absorbed his reality, that included its own version of the Tribunal too.
Only Thanos could possess the willpower and cunning to strike a bargain with God himself, and he is successful. Reality is restored with a new, more powerful Living Tribunal as its guardian, the threat of Annihilitus is neutralized, and Earth-616 Warlock returns to life. In this story, Thanos proves that he is not just a nihilistic man (which he can still sometimes be), but a creature of great understanding who cares about the cosmic balance. Thanos not only saves reality but is instrumental in the creation of the new version of the most powerful character in the Marvel Universe, the Living Tribunal.
