One-Above-All is the supreme being in the Marvel Universe, and is often referred to as the creator of everything. It is an omnipotent and omniscient entity that exists outside of the multiverse, and is beyond the reach of any other being.
One-Above-All is not to be confused with the Living Tribunal, another powerful cosmic entity in the Marvel Universe. While the Living Tribunal is incredibly powerful, it is still subject to the will of One-Above-All.