I once read a book and the final chapter talked about the eventual conflict between Jesus and the anti-Christ (which is basically Satan in human flesh). And Jesus only needed to speak in order to "win", so I can't think that the final judgment of Satan will be any different.
Hemistage will suddenly OD on big b00bs, then argue with Gemballa. His faulty machinery will commence a flame war, which will cause him to have a massive massive backfire which will crush the earth.
Other: The world will go through a second dark age of syndicalism and moderate anarchy. Big guys will wipe out the little guys who will atleast decimate the big guys back. After a period of general mayhem, disorder and complete lack of progress: the next stage of our society. Hopefully the last, a very long and prosperous one as well. After which we have no use of this world any longer and we... simply leave. The world will revert back to a natural state and await the sun to run out and leave this planet a barren, scorched and in the end a frozen rock.