Who could be the main antagonist in a Young Justice Ghost Girl Fanfiction?

The League of Shadows could be a great antagonist. They might see Young Justice as a threat to their plans in the world and Batgirl as an obstacle in Gotham. They could try to manipulate situations to make Young Justice and Batgirl turn against each other while they carry out their own devious plans, like releasing a dangerous virus in a major city.

Maybe a villain from the dimension where Wally has been. This villain could have followed Wally back to seek revenge or to take over the world that Wally has come back to. Since Wally has some knowledge about this villain, it would be his responsibility to stop the villain and protect his friends and the world. The villain might have powers that are a match for Wally's, making it a really tough fight.

A new, original character could be created as the antagonist. Maybe a powerful and vengeful assassin who has a grudge against Robin for some past event. This character could have unique abilities and a personal vendetta that drives the conflict in the fanfiction.

The Joker could be a great antagonist. He might have captured Robin for his own twisted games and is holding him hostage in some elaborate death - trap. The Young Justice team would then have to outwit the Joker to get Robin back.

The Reach could be a great antagonist. They might see Kid Flash's return as a threat to their plans for Earth. They could try to capture him and study his powers to find a way to counter the other heroes. Since they are an alien race with advanced technology and devious plans, they would pose a significant challenge for the 'Young Justice' team.

It could be a new villain who has a vendetta against speedsters. Since Wally is a speedster, this villain might see his return as an opportunity to prove himself. Maybe he's a scientist who has developed a weapon specifically designed to counter speedsters' abilities.

Perhaps an outside force that manipulates the Young Justice team into going against Naruto. This could be a villain who wants to create chaos in Naruto's world. The Young Justice, being unaware of the manipulation, start acting in ways that piss Naruto off. In this case, the real antagonist is the behind - the - scenes villain, but the Young Justice members end up being the ones Naruto has to deal with directly, making them sort of antagonists in Naruto's perspective.

A tech - genius named Techno - Tyrant. He could be a former game developer who turned evil after his creations were rejected. He uses his knowledge of gaming mechanics and virtual reality to create dangerous traps for the Justice League.

Lex Luthor could be a great main antagonist. He might see Izuku as a threat to his plans, especially if Izuku's unique abilities and sense of justice start to disrupt Luthor's schemes in the combined universe. Luthor could try to manipulate events to turn the Justice League against Izuku or find a way to steal Izuku's power for himself.

It could be a powerful ghost that has somehow made its way into the Young Justice universe. This ghost might be after some powerful artifact that exists in the Young Justice world and Danny and the team have to stop it.