Sivana may be the main antagonist, but it’s easy enough to imagine a scenario where either accidentally or on purpose, he unleashes the Seven Deadly Sins.
It was also confirmed last month that the Seven Deadly Sins (Pride, Envy, Greed, Wrath, Sloth, Gluttony and Lust), who can be briefly be seen in their stone forms in the Wizard’s base, the Rock of Eternity, will also end up causing trouble in Shazam! It remains to be seen how they’ll be freed, but one would assume Dr. Thaddeus Sivana is behind it.
Knowing them, they could have promised to give him even more power, leading to them either combining their power was his to make even mightier or just betraying him.