Justice League is the most powerful and popular superhero team in the DC universe. Even though people best know the Trinity — Superman, Batman, and Wonder Woman — the team has had many members over the years. And not all of them were always the good guys. Sometimes, either due to personal decisions or unforeseen circumstances, the previously heroic Justice League members turned evil.
Considering the extent of their powers, they were able to do a lot of damage until other superheroes managed to stop them or bring them back to who they once were. The history of DC Comics, as well as movies and TV shows, offer more than one example of Justice League members who turned evil, and caused even more harm than some villains did.
6 Green Lantern
Unlike other superheroes, who knew exactly what they were doing when they turned evil, Hal Jordan (aka Green Lantern) wasn't entirely responsible for his transformation. He switched sides when the ancient entity Parallax, which focused on fear, took hold of him.
As a result, Hal's light turned yellow. He attacked the Green Lantern Corps, his former co-workers and partners, and started killing them. Fortunately, Hal eventually became himself again and returned to his position as the Green Lantern, proving that sometimes superheroes could overcome the forces that took control of them.
5 The Flash
Multiple people held the title of the Flash over the years. One of them, Wally West, turned evil for a time. This happened when Wally came back the Rebirth series, but he could still remember events from the past universe. That caused him to snap, and he started killing people. The good news is that Batgirl, Booster Gold, and even Harley Quinn joined forces in order to stop Wally, and they succeeded.
Another speedster who turned evil was Barry Allen in the TV show The Flash. In the third season, the main villain was a mysterious speedster called Savitar who was about to kill Iris, unless the team figured out a way how to change the future. It was eventually revealed that Savitar was none other than an evil version of Barry from the future. Luckily, the team managed to stop this future Barry. The present Barry went on to build a different future, with his now-wife Iris by his side.
4 Shazam
A bit similar to his fellow Justice League member Green Lantern, Shazam also wasn't responsible for his turn to evil. Billy Batson, his human alter ego, is a child, good and innocent. That didn't stop Lex Luthor from taking control of the now-adult Billy in the graphic novel Kingdom Come.
By his clever manipulation, Luthor achieves his goal and has Shazam fight Superman. Considering how strong Shazam is, he almost manages to kill the Man of Steel. Fortunately, Shazam eventually manages to free himself from Luthor's control, but the story doesn't have a happy ending for him nonetheless. In order to stop Luthor from killing all metahumans, Shazam sacrifices his life and detonates the bomb that Luthor designed in order to achieve his evil plan.
3 Superman
Superman is the epitome of good. He represents truth, justice, and the American way, just like Captain America does in the Marvel universe. So when Superman fell and became evil, the change was even more devastating, considering his enormous powers. When the Joker tricked Superman into killing his pregnant wife Lois Lane, which led to the destruction of Metropolis, Superman snapped and killed the Joker.
Subsequently, he decided nothing like this would ever happen again and started ruling the world with an iron fist. While some superheroes were alright with it, others protested... and Superman wasn't above killing those who stood against him. The iconic Injustice comic book storyline has also been adapted into an animated movie Injustice in 2021.
2 Wonder Woman
Superman wasn't the only member of the Justice League who turned to evil in the Injustice series. While some of Superman's former friends and allies opposed him (such as Batman), Wonder Woman wasn't one of them. The Amazon Princess joined forces with Superman instead, even if it meant watching him punish those who disobeyed.
Wonder Woman supported Superman regardless of how many people he hurt, which spoke volumes about her loyalty to her close friend ,but also showcased her downfall from a hero to a villain. That was something that the readers didn't expect from Wonder Woman before it actually happened.
1 Hawk
While not a member of the Trinity, Hawk joined the extended Justice League. For the most part, Hawk fought evil just like every other superhero. But the Armageddon comic book storyline had him become a villain called Monarch, even though the real person underneath the moniker was originally supposed to be Captain Atom.
Despite that, Hawk turned into Monarch and when he gained the power to rewrite time after taking on Waverider, he was free to do what he wanted...until he died when a plane crashed.