Dr. Strange vs. DC EARTH.
Dr. Strange has access to all of his artifacts... and the 6 infinity gems (unable to be used together, but he has them anyways).
Assuming Spectre does not interfere. Can Strange take over all of DC earth.
1 day of Prep. Thats it. He has crossed the astral plane into DC earth and noone knows he's there.
And individually the gems can be used, they can not be combined. And for this fight, they work even in DC.