Title sort of says it all. Coming off of Shazam's success, what could be DC's overarching plot/arc that would tie the larger cinematic universe together? Who would be the big bad that unites them all?

The obvious answers would probably be either:

1) a film saga based on COIE with Anti-Monitor as the main villain or
2) something based on Final Crisis with Darkseid as the main villain

What about you guys?