Snyder's Evil Superman is Risky (But Justice League 3 Will Pay)
Zack Snyder intended to make Superman evil in the Justice League sequel, a divisive storyline that would have paid off in Justice League 3.

Superman could have turned evil in Zack Snyder's Justice League arc, and Justice League 3 could make it work. Man of Steel is Zack Snyder's second DC movie after the adaptation of "Watchmen", and its original intention is not to start the shared universe, but Christopher Nolan's "Dark Knight" movie mode could have Become the first work of the Superman trilogy. However, following the success of the Avengers and the MCU, the Man of Steel sequel was recast as a Batman-Superman crossover, which set the stage for the Justice League movie. Therefore, Snyder's Superman story had to be adapted.
Although the DCEU, which has since been renamed the DCU, quickly expanded to include other films such as Suicide Squad, Wonder Woman, and Aquaman, Snyder envisioned five films ranging from Iron Man to Justice League 3. movie arc. Justice League was originally conceived as a two-part film, but was later adapted into a more standalone story that introduced the Justice League and set up their confrontation with Darkseid and Apocalypse. Much of what Snyder planned for his Justice League arc was in Zack Snyder's Justice League, the Snyder cut, including hints at what an evil Superman would look like.
How Man Of Steel & BvS Set Up Snyder’s Evil Superman Storyline

While Man of Steel was not initially intended to draw on the Justice League story, elements from the first DCU film may find their way into future Justice League films. Foremost among these is the Codex, the key to restoring Krypton combined with Kal-El's DNA before the planet's destruction. In Zack Snyder's Justice League, Darkseid is looking for the Anti-Life Equation, which the villain later recalls has always been on Earth. However, depicting the Anti-Life Equation has been far from easy for DC animated films, shows, and even comics, and the concept often varies from author to author.
Darkseid could have used the Anti-Life Equation against Superman - and it would have worked. Snyder might use the Codex storyline to better explain how the Anti-Life Equation works for Superman, and why transforming Kryptonians is so important to Darkseid's plans. Man of Steel would also end up setting the scene for the events of Justice League 2 and 3, especially the scene where Superman sees his world burn to ashes as he descends into hell A Skull Crater Granted, the scene references Zod's Earth terraforming plans, but it can be traced back as a foreshadowing of the Justice League.
That being said, the biggest setting for the Sinister Superman storyline is in Batman v Superman: Dawn of Justice. Unlike Man of Steel, Batman v Superman was written for the Justice League movie. In fact, a lot of the criticism of Batman v Superman has to do with how the movie suppressed the presence of characters like Wonder Woman, The Flash, Cyborg, and Aquaman, who immediately made their way into Justice League. Still, when it comes to Superman's story, Batman v Superman teases that Superman will become evil because of what happened to Lois Lane through the vision of the future that Bruce Wayne created for The Flash.
How & Why Superman Would Have Turned Evil In The Snyderverse

In the Batman v Superman nightmare scene, an evil Superman who is about to kill Batman and his allies claims that Bruce Wayne "took her from him", possibly referring to Lois Lane. In Justice League 2, Darkseid would kill Lois Lane with his Omega Beam, first revealed by Zack Snyder at a fan event and later incorporated into Zack Snyder's vision of Justice League order from the future. Lois Lane should be in the Batcave when Darkseid kills Lois Lane, which means Batman won't be able to protect Lois. That's why Superman blames Bruce Wayne for Lois Lane's death.
However, unlike the popular video game storyline of injustice, Lois Lane's death does not in itself cause Superman to become evil. Instead, Superman would succumb to the Anti-Life Equation, as Zack Snyder teased in Justice League. In other words, the Anti-Life Equation would allow Darkseid to control Superman. As a twisted way to celebrate victory, Darkseid would have Superman don the classic red and blue suit, only to end up as Apokolips' most dangerous champion on Earth. That's why Superman leads an army of demons in Batman v Superman - when he's already working for Darkseid.
Thus, Snyder's split villainous Superman storyline would never have Clark Kent actually choose to be the villain. Snyder's Superman wouldn't be an injustice scene where Superman loses faith in the world after the Joker's most brutal plans. Man of Steel may be off to a controversial start for Superman's DCU journey, Because it ended with Superman choosing to kill Zod to save a family. However, the fact that the DCU's Superman could be seen as a more hopeless and insecure version of Kal-El has nothing to do with why Superman turned evil in the Justice League sequel.
How Superman Would Have Returned In Justice League 3

The nightmare scene in Batman v Superman and Zack Snyder's Justice League is not just a tease of what might have happened - the Nightmare timeline will indeed appear in the Justice League sequel. The Justice League won't be able to defeat Darkseid and his army, and the battle will end with Lois Lane's death and Superman joining Darkseid. As revealed in Zack Snyder's Justice League, Aquaman and Wonder Woman would also die during Darkseid's invasion. That's why Batman, Cyborg, and The Flash have to join the ranks of Injustice League members (like Mera) and villains (like Deathstroke and The Joker).
Batman's resistance, which also includes non-superheroes such as the soldiers in the Knight scene of Batman v Superman, will be Earth's only hope against Superman and Darkseid's army. However, with such a small group of heroes and villains, there is no chance of defeating the Anti-Life Superman. For example, in the Batman v Superman dream sequence, Batman has seen himself killed by Superman. The only way for Batman Resistance to save the planet is to bring back Superman, which can only be done while Lois Lane is still alive. The mission was supposed to be simple: send The Flash back in time in Justice League 3 to prevent Lois Lane's fateful death.
Snyder's Superman Story Can No Longer Happen

The Anti-Life equation Superman storyline is presented only as part of Snyder's Justice League arc. The story involving Darkseid and Apocalypse is a Justice League-level event, which means it has to involve the DCEU Justice League movies and their heroes. However, there are currently no plans for a sequel to Zack Snyder's Justice League. In fact, with James Gunn's plans for DC Studios, the Snyderverse has come to an end. The best hope for Superman's story to continue in the DCU is Iron Man 2, which is still rebooting despite Cavill's cameo in Black Adam.
Among those on the slate is Superman. In the initial stages, our story will be focusing on an earlier part of Superman's life, so the character will not be played by Henry Cavill.— James Gunn (@JamesGunn) December 15, 2022
Superman's cameo in Black Adam itself confirms that the Snyderverse Superman story didn't happen. Superman wears the classic red and blue suit in Black Adam, which Superman only wears in the Snyderverse Controlled by Darkseid's anti-life equation. With James Gunn working on a new Superman movie that won't star Henry Cavill, it's safe to say that the Snyderverse planned during Batman v Superman is over. Henry Cavill won't be returning as Superman in James Gunn's DCU, and the next Superman movie will follow a younger version of DC's most famous superhero.