Which post Molecule Man you are talking about, Evil Molecule Man persona that almost cause the Multiverse to collapse on itself when fighting Beyonder would annihilate Exitar. Passive Molecule Man that Sentry defeated, yes he will get stomp into sh**.
There's only one MM post retcon. He lost to Klaw, lost to Aaron, lost to and was killed by Sentry. He beat Kosmos/Beyonder. That's it.
PS when did it cause the multiverse to collapse? If you are referring to their battle spanning multiple layers of reality, big deal. Prof X/Dark Phoenix did the same, Aaron/Uatu did so too, Odin/Seth did it, Mephisto/Satannish did it, etc...
He had ONE good fight and lost EVERY OTHER fight he was in. So 75% of the time he was trash.
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..even the outer hells are indifferent matters for they bow only to potent and archaic Nodens.