Galactus
Who would have been able to give Galactus as good of a fight as All Father Thor did when they had it out in the future?
It has to be that version of Galactus. It can't be a slaughter, because I want to know which character, in your mind would be able to do just as good against him without judging it solely based on the tier system.
No BFR
Just a full out war.