Batman would definitely be one of the most affected. He's used to dealing with normal threats in Gotham, and Naruto's supernatural abilities would be a huge challenge. Another would be the Flash. Naruto's clones could potentially surround and confuse the Flash. Wonder Woman too. She's a warrior, but Naruto's unorthodox fighting style and his array of jutsu would be difficult for her to counter immediately.
If Naruto becomes a villain in the DC crossover, he might set his sights on Superman. Naruto could believe that Superman's power is a threat to the balance he wants to create. He would use his ninjutsu to try and take on Superman. For example, he could use his Rasengan, a powerful spinning ball of chakra. However, Superman's strength and heat vision would be tough for Naruto to overcome. This would lead to an epic battle between the two, with the other DC heroes and Naruto's possible allies getting involved as well.
If Naruto loses all his friends in a tragic way, perhaps in a battle against an overwhelming enemy that the village could have prevented. His grief could turn into hatred towards the shinobi system. He may decide that the existing order is what causes all this pain and destruction, and then he starts to work against it, becoming a villain in the eyes of the village.
In this kind of fanfiction, Naruto becoming the Juubi would completely change the Naruto universe. It would mean he has an insane amount of power. He could potentially reshape the world, bring peace in a way no one expected. His relationships with other characters like Sasuke would also be very different. Sasuke might be both in awe and a bit jealous of this new power Naruto has.
Definitely Naruto and Superman. They are both iconic characters in their respective universes. Their different power sets make for an interesting comparison. Another popular crossover is between Sasuke and Batman. They both have a dark and brooding side. And of course, Sakura and Wonder Woman. The contrast between Sakura's ninja skills and Wonder Woman's superhuman abilities is appealing.
One interesting concept is the power clash. Naruto has his ninja powers and the DC villains have their own unique abilities. Seeing how they interact and compete is really exciting.
His confidence could turn into over - confidence bordering on arrogance. As a villain, he might think he is above everyone else and that his way is the only right way. He would no longer listen to advice or consider the consequences of his actions on others, believing that he can handle any situation on his own, no matter how dangerous or unethical.
It could be Kabuto. Since he has a lot of knowledge about medical ninjutsu and experiments, he might see Naruto's robotic form as a threat or something he can use for his own evil purposes. He could try to control Naruto's robotic functions and turn him against his friends.
One popular 'naruto dc villain fanfiction' is 'Naruto in Gotham'. It's an interesting take on Naruto finding himself in the DC universe and dealing with its villains. Another is 'Naruto vs. The Joker' which has some really cool fight scenes.
In 'naruto crossover dc fanfiction', an exciting concept is the team - up possibilities. Picture Naruto and Green Lantern working together. Naruto's determination and willpower could be seen as similar to what powers the Green Lantern ring. Also, the idea of jutsu being used in the DC universe is cool. A Naruto character could use a clone jutsu in the middle of a fight in Gotham, confusing the villains. And the cultural exchange between the two universes, like Naruto introducing ramen to the DC heroes, is a fun concept too.