Apparently responsible for the existence of all life in the Multiverse and possibly beyond, the One-Above-All is the master and sole superior of the cosmic overseer and arbitrator known as the Living Tribunal.
When the pregnant Susan Storm feared for her husband's possible death at the hands of the "all-powerful" Silver Surfer, Uatu the Watcher tells her that there is only one being that is truly "all-powerful", and that "His only weapon...is love!" During an encounter with the Sorcerer SupremeDoctor Strange, the cosmic entity Eternity tells Strange: "I and my brother, Death, comprise all of your reality, mystic! Neither he nor I are God, for God rules all realities!" When Thor once compared himself and Odin to various other gods and abstract beings in terms of power, he notes: "...and 'tis said that a being, called the Living Tribunal—the final judge—hath the power to enforce his will 'pon any cosmos he doth judge! And 'tis said his power is supreme in all the Multiverse. Even I, son of one of the mightiest of all gods, find it impossible to conceive of such levels of power! And 'tis a humbling thought to consider how much greater the Creator of all Universes must be than that of all of His creations combined!"
The Cosmic CubeKubik on a tour of reality displaying various higher powers to Kosmos, upon meeting the Tribunal, tells her that while it is the most supreme power which can be comprehended, "Logic would indicate that the Tribunal itself is but another servant, but of what none dare imagine." In the aftermath of the events of Infinity Gauntlet, the Living Tribunal easily undoes all the destruction an enraged Adam Warlock wreaks at his Trial, claiming that, "I represent forces that dwarf even your might. My authority comes from on High." When the Protégé claims to the Living Tribunal and other cosmic entities that he is the most powerful being that ever was, and that he will surpass them all and move up, the Tribunal counters, "Impossible! There is only one above the Living Tribunal!" Later, after the Protégé declares himself the One-Above-All in an attempt to seize ultimate power, the Tribunal absorbs the Protégé into itself, proclaiming, "Your actions and intentions are inexcusable! Make your peace! May the One-Above-All forgive you!"
Thanos realizes that the One-Above-All has subtly manipulated him into destroying and recreating the Universe using its Heart in order to fix a fundamental flaw. The One-Above-All seemingly appeared to the Fantastic Four in "Heaven", at the time of the Thing's death, praising them for their persistence in exploring the Marvel Universe and promising extraordinary new wonders to be discovered in the years ahead, and eventually restores the Thing back to life. A grieving Peter Parker was encouraged by the One-Above-All, disguised as an elderly homeless man, to keep faith, when his Aunt May lay close to death. When a bartender asks the demon Mephisto whether the Living Tribunal, having created the Infinite Embassy, was actually "God", Mephisto responds, "No, he's not God. He's just the biggest kid in all the playgrounds. And if he knows the Principal, he's not exactly chatty about it."