It could be a variety of villains. Maybe some of the traditional Naruto villains like Orochimaru or Pain could be in the story and Naruto kills them. Or perhaps in this fanfiction crossover, there are new villains created that are a combination of Naruto - style threats and Justice League - type menaces. It's hard to say exactly without reading the fanfiction, but it would be interesting if it included some well - known Naruto baddies being taken out by Naruto in a new setting with the Justice League around.
In this fanfiction, Naruto's power is a force to be reckoned with. He has a vast array of ninjutsu skills at his disposal. The Justice League members, on the other hand, are a mix of super - humans and meta - humans. Superman's strength is almost limitless, and Aquaman has his control over the sea. Naruto's ability to defeat villains in this context might put him in a position where he has to prove himself against the Justice League. His shadow clone jutsu could potentially overwhelm some of the League members in terms of numbers, but they have their own unique ways of countering such attacks. It really depends on how the story unfolds and how the powers are balanced in this crossover fanfiction.
Well, it could be that Naruto uses his shadow clone jutsu to overwhelm the Justice League members. Maybe he'd start with Batman, using his speed and clones to catch him off guard. Then for Superman, he might use some of his more powerful jutsu like the Rasengan, powered up with Sage Mode. But it's really a wild and crazy concept as the two universes are so different in power scales and nature.
Well, one possibility could be that Naruto's powerful ninjutsu skills give him an edge. He might use his Shadow Clone Jutsu to confuse the Joker and then land a fatal blow with a Rasengan. Another aspect could be Naruto's strong sense of justice which drives him to take out the chaotic Joker in the Justice League universe.
Lex Luthor could be a likely villain. He's always devising plans to take down the Justice League, and this time he might have come up with a scheme that almost succeeds, until Batman steps in. For instance, he could create a super - weapon that targets the unique powers of each Justice League member.
Another one is Goro. He's a petty thief in Naruto fanfiction who has a special skill of being able to blend into the shadows. He steals from local merchants in Konoha. Goro may not seem like a big threat at first, but his actions can sometimes lead to bigger problems, like when he steals important items that are needed for a mission.
Occasionally, in alternate storylines or specific comic series, Batman has been depicted killing villains. However, this goes against his traditional code of not taking a life in the main continuity.
One could be Ozai from Aang's world. He might be even more powerful in this fanfiction and Naruto has to step in to help Aang deal with him. Naruto's unique skills and abilities would be crucial in countering Ozai's firebending.
The villagers of the Land of Waves would surely support Naruto. They have suffered a great deal under Gato's rule, so they would see Naruto as their savior. Also, Sasuke might support Naruto. Even though they have their differences, Sasuke would recognize the need to stop someone as evil as Gato.
Darkseid is another possible villain. He is extremely powerful. He could send his minions to attack the Justice League first, weakening them, and then use some sort of magic or technology to trap them. Batman would then have to find a way to free the League from Darkseid's clutches, perhaps by finding a weakness in Darkseid's power source.
Definitely Orochimaru. He has great power and knowledge, and if Naruto could convince him, he would be a valuable ally. Another one could be Pain. Since Pain had his own ideology about peace, Naruto could find common ground with him and unite him.