So with Dwayne Johnson cast as Black Adam, I decided to research the character and his history with Captain Marvel (Shazam), and was surprised to find out that, despite his history/incredible powerset, he's not Billy's archenemy. Why is it Dr. Sivana?

I think because Sivana is more of a challenge and is very persistent.

Because he present more of a intellectual challenge for Billy.

@redsupes: He's the antithesis of Billy. Billy being young, optimistic and good natured, while Sivana is old, bitter and evil. Also, he is essentially CM's equivalent to Lex Luthor.

It's also great that he has a family so you have the perfect family feud in Sivana, Sivana Jr. and Georgia against Billy, Freddy and Mary.