I think they raised the stake so many times it the obvious conclusion. When the show started killing demon's was really hard. Yellow eyes and Lilith quickly took the place of ordinary demon on top of the food chain. Then the angels showed up and for a while they were the one thing the Winchester could not really kill. After that we got Lucifer, the super saiyan 5 bad Castiel arc, Leviathan, Crowley and the mother of all monsters. Now Crowley was their prison bitch for months the last knight of hell is dead and angels are dying left and right. Either God is next on the list or Death.
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