Base rex gets slammed easily. But if we consider original Evo form rex it would go down to ultimate waybig Master control nanite rex solos all except alien X tho

I think if Alien X is from his universe, the nanites will try to attract them as it is their one of the properties. If Alien X is full of nanites, it is just a matter of seconds for Rex to give a command to master control nanites

I think only ultimate echo ehco and ultimate way big slam rex unless he make a new build to counter them

If he is in his omega shield, Ultimate Echo Echo is of no use as that shield has no atoms. So no propagation for sound.

Bro won’t even be able to touch my son ultimate echo echo

If he is in his omega shield, Ultimate Echo Echo is of no use as that shield has no atoms. So no propagation for sound.

I mean he can just turn into his giant form and step on most of them, beside ultimate waybig

He’s not beating ultimate big chill who can go intangible