Who could be the main antagonist in 'naruto becomes a monster fanfic'?
The Akatsuki members could also be antagonists. They might see Naruto as a threat even more so when he becomes a monster. They could try to either kill him or capture him to use his new monstrous powers for their own goals, like collecting tailed beasts.
It could be Orochimaru. He has always been interested in experimenting with new forms and powers. If Naruto becomes a monster, Orochimaru might see him as a perfect specimen to study or use for his own evil plans.
Who could be the main antagonist in a 'Naruto the Monster Rancher' fanfic?
It could be Orochimaru. He's always interested in new forms of power. In this fanfic, he might discover the Monster Rancher world and try to use the monsters there for his evil experiments and plans. He could be trying to create some sort of ultimate monster by combining the powers of the Naruto universe and the Monster Rancher monsters.
Who could be the main antagonist in 'naruto becomes a heartless fanfiction'?
It could be Sasuke. If Sasuke has turned completely to the dark side and Naruto fails to save him, Naruto might be so frustrated and angry that it starts to make him cold - hearted towards everyone. Sasuke's actions could be the trigger for Naruto's transformation.
Who could be the main antagonist in 'naruto becomes a ghost fanfiction'?
It could be an evil spirit that wants to use Naruto's new ghostly form for its own dark purposes. Maybe it tries to control Naruto and make him do evil things.
Who could be the main antagonist in 'naruto becomes a berserker fanfiction'?
It could be Orochimaru. He's always been interested in dark and forbidden jutsus. He might see Naruto as an interesting experiment and use some dark magic on him to turn him into a berserker just to see what chaos he can cause in the ninja world.
Who could be the main antagonist in 'naruto becomes a wraith fanfiction'?
It could be Sasuke. If Naruto becomes a wraith, Sasuke might see him as a threat to his own power - seeking goals. Sasuke could try to eliminate Naruto in this new form, thinking that Naruto is now too dangerous or has strayed from the path he believes in.
Who could be the main antagonist in 'naruto becomes immortal fanfiction'?
It could be Orochimaru. Since he has always been obsessed with immortality and power, he might see Naruto's new - found immortality as something he wants to steal or study. He could use his dark jutsus and his army of followers to try and capture Naruto.
Who could be the main antagonist in 'naruto becomes the shield fanfiction'?
It could be a new, powerful ninja from a far - off land who wants to destroy Konoha. This ninja might have a grudge against Naruto specifically and forces him to become the shield to protect the village.
Who could be the main antagonist in 'naruto becomes a wolf fanfiction'?
Perhaps it's a jealous ninja from another village. This ninja has always been envious of Naruto's power. So when he gets the chance, he uses a dark magic to turn Naruto into a wolf. His goal is to make Naruto weak and lose his status among the ninja community.
Who could be the main antagonist in 'Merlin becomes a dragon fanfic'?
It could be Morgana. She might see Merlin's transformation into a dragon as a threat to her own power and plans. So, she tries to stop him from fully becoming a dragon or tries to use his new form for her own evil purposes.
Who could be the main antagonist in 'sonic becomes a girl fanfic'?
It could also be a new villain that is specifically interested in Sonic because she is now a girl. Maybe a villain who has some sort of vendetta against female heroes or wants to use Sonic's new form for some evil experiment. However, Dr. Eggman is so iconic in the Sonic series that he would be a strong contender for the main antagonist role even in this fanfic scenario.