oblivion can't really be destroyed as he is nullification itself.
those caught in the blast of the ultimate nullifier go to his realm "the outer void", and when thanos erased half or the universe's populace, it can be assumed they were materialized there.
oblivion also survives the big crunch/bang process, actually it can't effect him = truly indestructible.(so did galactus but it was a melding of galan and the primordial energies that spared him)
unicron can't do squat to him.