I dunno about that. OKT is stronger then Odin. He did quite a bit better then Odin or Mephisto has traditionally done against Galactus. Mephisto ( assuming not current, in which hes fodder ), is also not on Skyfather level outside of his realm.
Dommy and Umar outside of their dimension likely cant either.
Classic Fate is rough. Mordru isn't ( Darkseid level ).
Maybe 7, certainly 8.
What? Current Mephisto has stomped the new Nebulon(Who's now powerful enough to control the Conductor, a being/god unlikely anything Galactus has seen before), is one of the most powerful beings in the universe by being part of a cosmic group which has members like Lady Death and Oblivion, created the very first Ghost Rider whose the same comic says the character is one of the strongest Prehistoric Avengers(Which Odin was a member too, mind you) and easily banished the spirit of Zarathos back to hell. He's way more powerful than his classic version by consistent feats/portray and is at least on the "Skyafther level", if not quite above.
Considering Dormammu already stomped Gaea while weakened in an inferior body, who an guidebook(Marvel - Absolutely Everything You Need To Know) has her ranked above Odin power-wise in a list of the most powerful gods, I would say he alone can do it.
Last I had checked Mephisto was a prisoner in his own realm or something like that. If that has changed, apologies. Even within his own realm, Mephisto had trouble against Galactus. He never got close to doing as well as OKT thor did.
The Conductor is just a celestial it seems. Certainly not anything Galactus hasn't seen before. Though, statements do seem to contradict that.