@GeneralVan: Oga had city level DC at the end though plus flight, lighting projectiles and good strength. Physically he might lose but factoring his range and mobility I think even Meruem could lose. If he didn't, he's the only one I could see taking Oga possibly.
I agree. I cannot see the logic in Spike being the better H2H combatant. HE is not in Revy's league of strength. He can have better reactions all he likes. He can't take her hits and probably not parry them for long if at all. The gun round I see as much more likely.