To make it fair, Monarch should have no collected energy underneath his nanoweave armor. He's just Captain Atom with damaged Dilustel skin, a lack of morals to hold him back, and slight delusions of grandeur. CA has shown the ability to repair his skin whenever damaged, so why he didn't do the same as Monarch is just silly. Anyway, Monarch simply has too much base power without factoring in his ability to draw energy from the Quantum Field with his will.
A fight between Monarch and Void would be great to see. IMO I don't think M got what it takes to permanently beat down a void that wants to kill you. He won't have a PIS effect him in this fight.
Thanos v.s SBP would be a long fight imo. But I think Void can kill Monarch before either of these to can kill each other.