In the video above, we dive into the history of Shazam, the adult alter ego of a teenage boy. Billy Batson transforms into the superhero by speaking the magic word "SHAZAM," an acronym for a spell that gives Billy the wisdom of Solomon, strength of Hercules, stamina of Atlas, power of Zeus, courage of Achilles, and speed of Mercury.
With these powers, Shazam has gone toe-to-toe with Superman and used the Man of Steel's weakness to magic to gain the upper hand. Most iterations of the Justice League have welcomed Shazam into their ranks, and in certain continuities, Shazam is a founding member of the League. Not many DC Comics characters know that one of the Justice League's strongest members is secretly still a kid, but those that find out typically accept the story instantly.
Despite his immaturity, Billy is a good kid at heart, which is why he was chosen to inherit the magic to transform into the hero Shazam from the ancient Egyptian wizard, Mamaragan. Billy initially went by the name Captain Marvel, but that was retconned to Shazam so DC Comics could avoid a trademark conflict with Marvel Comics' Captain Marvel (who's also about to get her own live-action movie).
Initially, any utterance of "SHAZAM" would transform Billy into the costumed crime fighter, whether he said it or not, which led to more than a few hilarious accidents in his early comic book adventures. However, this became problematic when his alter ego's name became Shazam, so the rules of the magic spell were changed so that Billy could only transform when he wants to.
Shazam is virtually invincible, so the easiest way to defeat him is before Billy can transform. Throughout his history, Shazam has really only been defeated because of his immature mind or by exploiting the method by which he transforms. More than one villain has been able to trick the man with the mind of a child. Also, characters who are observant enough have noticed that when Billy utters, "SHAZAM," he transforms by the magic striking him as a lightning bolt. So using a strong enough electrical current to simulate a powerful lightning strike can revert the transformation.
Shazam will be making his DC Cinematic Universe debut in the upcoming Shazam movie, scheduled to release April 5, 2019.