It seems there was at least one villain considered for Superman before Lex Luthor was selected. In a recent interview, James Gunn confirmed that Brainiac, was indeed in the running, at least initially.
"Brainiac was considered, yeah," admitted Gunn when asked about if any other Superman foes were in the running to be in the film during the early stages of development.
Brainiac ranks among Superman’s most formidable adversaries, a hyper-intelligent alien computer/alien with a chilling obsession for collecting knowledge.
Known for traversing the universe, he infamously shrinks and bottles entire cities to preserve them, while often wiping out the rest of the planet without remorse.
Armed with advanced alien technology and a mind far beyond human comprehension, Brainiac poses a uniquely cerebral threat.
Cold, logical, and utterly detached from morality, he challenges Superman not just physically, but intellectually (albeit from a more technological perspective), making him one of the Man of Steel’s most dangerous and enduring foes.
Gunn was then questioned as to whether Mister Mxyzptlk was considered. If you recall, in one scene, Superman casually tells Lois Lane that the Justice Gang can handle the situation because it’s “just a dimensional imp,” as Guy Gardner proceeds to repeatedly beat it with a giant baseball bat.
For sharp-eyed fans, this line seemed like a clear nod to Mister Mxyzptlk, the mischievous Fifth-Dimensional being known for causing chaos in Superman's world.
However, according to James Gunn, that wasn’t the case. Despite the obvious connection, Gunn confirmed that Mxyzptlk was never considered for the film.
The last villain the director was asked about was Bizarro and whether Ultraman could be brought back as the wayward, mirror Superman.
"Well, we'll have to see where we go next," said Gunn, admitting, "it's a very vague answer." When asked if he was being cagey because the question was nearing secrets for future plans, Gunn dismissed the notion, stating, "No, it means I just don't know what the hell I'm doing next."
Also recently, Gunn told Entertainment Weekly that Lex likely took Ultraman out of the oven a little too soon as his physical features are just slightly off. That sure sounds like the groundwork is being laid for Bizarro, especially if his time in the black hole further distorts his physiology.