Complete as in combination of all of his personalities. This is important not only because he gets all their powers but no low showings could be used against him, since in the past when he'd use a personality's power he would be sometimes susceptible to certain attacks like telepathy for instance.
Yes. Complete Legion would be David having merged and in control all his personalities as seen in Uncanny X-Men #24.
Thats him maximizing on over 1000 personas, more than 200 of them being omega level. And at least separate personas that can warp reality in a universal scale.
Legion's powers are explicitly open-ended since they include the ability to develop NEW ones (along with new personas). For example, a "complete" Legion might suddenly express Leech-like powers on a whim and nullify MoD's abilities.
But then again, MoD might just overpower and erase Legion before he has time to respond. Might go either way.
That seems to me as universal, though. Still, manipulating those quantum corals (parts of the multiversal construct) is extremely impressive. Not many are capable of warping reality with such ease.
He's a reality warper, that should give you a hint. Specifically though, inducing planck temperature did affect MoD. However, i did give MoD the win since he's established to have mastered reality enough to affect the abstracts.
MoD basically traveled "all of reality" and mastered it over the millions of years. "all of reality" in this context = omniverse (confirmed in the handbook). Which is why he was able to use even major abstract beings as his foot soldiers.
It's true, the only thing that could even weaken him was himself. And it still took an infinite number of Fantastic Four's (and one Doom) to finish him.
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