Annihilus vs Apoocalypse
Apoc gets a month of prep, and Annihilus gets none, and only knows as soon as the battle starts, of who he is fighting.
Apocalypse also get one horseman. Let's say Holocaust, and Mr Sinister.
They fight in the middle of the Annihilation Wave (Annihilus has no control over them). Say Apoc can breath in space to, and he doesn't have to adapt (along with his allies).
So, who wins?