Michael solos, LOL. First off, Dooms implied power says, that his durability is not that good. A explosion from 100k universes can kill every Beyonder, which just shows, that Doom is not that impressive. Michael Demiurgos can easily cause a attack, which can destroy the whole creation, when he dies:
Doom never showed infinite multiversal feats. He only has taken over the whole planet, oneshotted Thanos base, etc. That God Doom had problems with IG just shows how weak he is, lol. Superman is not that impressive either, because he was really harmed by a attack with the boold of 52 universes, which Michael easily can cause. A
Michael threatened to destroy the World Tree which is connected to every single Multiverse in DC's Snyder Omniverse to the point it even affected Lucifer's Creation for some reason. I still have gripes about that because I'm not sure why the World Tree affects a Creation outside of Yahweh's. But it just did.
But DC has come to the point where there are potentially infinite number of Infinite Dimensional Multiverses outside the Source Wall if the speculation is true that Perpetua's sisters and brothers tend to equal Creations outside the Main DC Multiverse (which is Infinite-D to Carey, Matteis and Jenkins). Which is something Michael almost destroyed.
Fact is, Michael can in fact solo this.
Doom has too many inconsistencies and stupidities to get around. But DC's evolving growingly ever united cosmology makes Marvel look pocket dimension by comparison.
Thought Robot Superman is powerful, but even if you united DC's Cosmology to scale for him against Michael, he still loses really badly because something like Perpetua is hinted to be above the Monitors in power, and that gal was sealed in the True Source Wall (above the Monitors) that was created by Michael in the first place.
Spectre on the other hand, he sometimes gets challenged by low level wizards, and then sometimes goes up to power in surpassing the Outer-Voids in power. It depends on which level we discuss here.