Who could be the main antagonist in a 'Peter Harry team up' fanfiction?

A group of rogue Death Eaters could be the main antagonists. They think that Voldemort has gone soft by teaming up with Harry. So they break away and form their own more extreme and violent group. They start attacking both the wizarding world and anyone associated with Harry and Voldemort's new alliance. Harry and Voldemort must then fight against their former allies who have become a greater threat than ever.

It could be a new character. Maybe a dark sorcerer who has come to Neverland while Peter was growing up. This sorcerer wants to take over Neverland and sees Peter, with his new adult understanding and power, as the only obstacle. The sorcerer could start to corrupt the island, turning the mermaids and Lost Boys against Peter, making him fight not only for his place in Neverland but also for the very soul of the island.

It could be a new villain who has somehow influenced Team Cap's actions. This villain might be using Team Cap as a means to achieve their own evil goals, and Peter Parker realizes this and tells Team Cap off for being so easily manipulated.

It could be a rogue ninja from a rival village. This ninja has a personal vendetta against Konoha and specifically targets Team 10 because of Naruto's presence. He might be jealous of Naruto's growing power and fame and wants to prove himself by defeating the team.

One possible plot could be that Peter and Harry are in a city facing a new super - villain. Peter is having trouble fighting the villain alone as the villain has some new technology that can disrupt his spider - sense. Harry, who has been working on some advanced gadgets in his Oscorp lab, teams up with Peter. Harry uses his gadgets to counter the villain's technology while Peter uses his acrobatic skills and super strength to take on the villain directly. In the end, they manage to defeat the villain and their friendship grows stronger.

Perhaps an old enemy of one of the members of Team 9 shows up. Since Naruto has joined the team, they might see it as an opportunity to get revenge. This antagonist could be someone who was once defeated by the member's family and now wants to prove themselves. They would be very cunning and use their knowledge of the team member's past to try and divide the team.

It could be Danzo. He's always been a bit of a shadowy figure in the Naruto series. Maybe he sees Naruto as a threat to his power and influence in the village and manipulates the situation so that Team 7 has to abandon him. He would be a great main antagonist as he has the resources and the motives to cause such a rift in Team 7.

It could be Orochimaru. He might see the baby versions of Team 7 as perfect subjects for his experiments. He could try to kidnap them to use their unique chakra or potential for his own dark purposes.

A powerful dark wizard could be the main antagonist. This wizard has been ruling the other dimension with an iron fist and sees Peter as a threat to his power. He uses his dark magic to create all kinds of obstacles for Peter, from summoning monsters to casting spells that distort Peter's perception of reality.

A powerful and corrupt organization might be the main antagonist. They blackmail Wade into kidnapping Peter. The organization wants to study Peter or use him as a bargaining chip. Wade is caught in a difficult situation where he has to protect Peter from this organization while also dealing with the fact that he has kidnapped him.