Who could be the main antagonist in 'Return of the Dragon Rider fanfiction'?

It could be a powerful dragon hunter. This person would see Naruto's dragon as a prize to be captured or killed. They might have a personal vendetta against dragon riders in general.

It could be a dark wizard who wants to control the dragons for his own evil purposes. He might see Harry as a threat because Harry is forming a bond with the dragons and teaching them to resist dark magic.

Perhaps a powerful sorcerer who wants to capture the black horse for his own dark purposes.

It could be Orochimaru. He is always seeking power and the strange and powerful abilities of the Ghost Rider might be something he desires. He could try to capture or study the Ghost Rider to gain an edge in his own plans for power and immortality.

A powerful dark wizard from the human world who has found a way to cross over into Equestria. He wants to harness the magic of the Elements of Harmony to increase his own power. He sees the Ghost Rider as a threat to his plans and tries to eliminate him while also causing chaos in Equestria.

A good antagonist could be a character from the 'Resident Evil' universe, like Albert Wesker. His superhuman abilities and evil plans for global domination would pose a huge threat to Alex Rider. Alex would have to use his wits and skills to stop Wesker's bio - terrorist plans.

It could be a powerful and shadowy figure from Wolf's past, like an old military commander who has gone rogue. This person might have a vendetta against Wolf for some past betrayal and sees Alex as a way to get to Wolf, using Alex's importance in the spy world as leverage.

It could be a former ally of the Pokemon Master who has turned evil. Maybe they felt overshadowed by the Pokemon Master and now seek revenge. For example, they might have found a dark artifact that corrupts them and gives them the power to control other trainers' Pokemon.

It could be a powerful devil who sees the Ghost Rider as a threat to his plans in the school. Maybe this devil wants to take over the school or gain more power among the students, and the Ghost Rider's presence and his sense of justice stand in the way.

A powerful and corrupted former Kamen Rider could be a great antagonist. Maybe someone who was once a hero but was consumed by power and now wants to take over the world using their Rider abilities for evil. They would know all the tricks of the trade and be a formidable foe for Phantom.