Galactus is well fed, no prep time and to the death
ITS ALWAYS speculation. theyve never fought eachother in comics so of course its ALWAYS speculation. thats what this board is. SPECULATION. It'd be stupid if they had a board called battles and only allowed you to talk about battles that already happened in comics.
Total speculation. We haven't seen the upper limit of any one of these three characters.
Galactus is obvious at around Eternity level (full feed), can't say the same to rune King Thor and Golden Super...
If that is the case, when characters are at that level (Abstracts), they aren't really battling in the conventional sense (w/firsts and energy blasts) they are simply willing changes to reality or using other lower entities to further their goals.