Sivana: Doctor Thaddeus Bodog Sivana is the evil criminal, mad scientist of the SHAZAM world, occasionally likened to Superman's Lex Luthor because he too is a bald, criminal genius. The image of Sivana was purportedly based on that of C.C.Beck's neighbourhood pharmacist. In the 1987 mini-series, Sivana is Billy Batson's uncle, who killed Billy's parents for insurance money which would fund his own research. In the Power of SHAZAM graphic novel, Sivana is Billy's half-uncle (Billy's father's half-brother) who funded the expedition which got Billy's father killed and afterwards kept Billy's inheritance to fund his own business ventures. Sivana was also the one to coin the phrase "big red cheese" to describe our hero.
The Seven Deadly Enemies of Man: Pride, Envy, Greed, Hatred, Selfishness, Laziness and Injustice. These evil spirits that plagued mankind have been imprisoned by SHAZAM in the statues that line the passage way to his throne. Notably, the seven enemies of man should not be confused with the seven deadly sins. In comparing the seven enemies to the seven sins, notice that the sin "Lust", has been replaced by "Injustice" in the enemies - presumably in deference to the G-rated audience. :-)
The Three Faces of Evil: Terror, Sin and Wickedness. Three incarnations of evil imprisoned by SHAZAM in the Rock of Eternity.
Mister Mind: This villainous worm first appeared in "The Monster Society of Evil" - a whopping 25-part serial published 1943-1945. Billed as "the most evil mind in the universe", Mister Mind was an alien worm capable of mentally possessing others and bent on world domination. In the 1990's series, Mister Mind was one of a race of Venusian worms with strange mental powers, including possession and telekinesis. When the rest of his race were destroyed by Captain Marvel (who lured them unprotected into deep space via a Boom Tube), Mister Mind inherited the cumulative powers of his entire race's group mind.
Black Adam: Black Adam, originally called "Teth Adam" was the first champion upon whom SHAZAM bestowed his powers, in ancient Egypt. At first, Adam fulfilled his role admirably, but was eventually corrupted by his powers and turned on SHAZAM, who stripped him of his powers. Of course, Adam regained his power in the 20th Century. In terms of power, Black Adam is the equal of Captain Marvel.