9. Black Adam - Shazam
Because Black Adam is Shazam's nemesis, everyone was expecting him to play a prominent role in the live-action film. And since Dwayne Johnson was already cast (waaaaaay back in 2009 for a completely different production and again in 2014 for the DCEU), his appearance in David F. Sandberg's Shazam seemed like a sure thing.
Apart from popping up as a hologram for a few seconds, the black sheep of the Marvel family was nowhere to be seen in Shazam. Although Adam was meant to be the antagonist, he was substituted for the wicked scientist, Thaddeus Sivana. As mentioned on Collider, the producers believed Adam's backstory was so complex, it would be been better to introduce the character in his own film.
Shazam actor, Zachary Levi, said it was a good move not to introduce his arch-enemy too early since the franchise would have nowhere to go. At the moment, Shazam and Adam aren't set to cross paths until the third movie in the series. But due to the uncertain future of the DCEU and Adam's solo film being delayed (again), it's not clear when the champions will meet.