DC's pantheons VS the Celestials
It always seemed the case that Earth's pantheons in the MU could never do anything to stop the Space Gods. Three sky fathers combined were described as "gnats" compared to a Celestial who wasn't even the biggest of his kind. Celestials' power is simply beyond that of these pantheons and I believe it may also have been depicted to be above Galactus as well. But the Celestials now decide to do their stuff in the DCU. No cosmic entities (the Endless, the Specter, 5-D Imps, etc) can be involved in any way.
All of DC Earth's pantheons, including the New Gods (with Apokolips and DS maybe having something to do with it), must find a way to stop the Celestials from destroying Earth. If they can't stop them, the Celestials will systematically attack each home realm of each pantheon until either the Celestials are stopped or all of DC's pantheons and their home realms are destroyed. Earth's heroes and villains can't be involved in any way.
1st scenario: As much prep time as Marvel Earth's pantheons had.
2nd scenario: No prep time.
3rd scenario: The pantheons have the Asgardian Destroyer and are allowed to project their souls into it to power and control it to attack the Celestials. Will they fare better than Marvel's Asgardians did? Also, the Destroyer does of course have the Odinsword.
4th scenario: Same as 3, but the Destroyer has Marvel Surtur's Twilight Sword instead of the Odinsword.