Who could be the main antagonist in 'Hwrry Potter discovers chakra fanfiction'?

One possible plot could be that Harry Potter, while on one of his adventures outside of the wizarding world, stumbles upon a hidden group that practices chakra. They initially see him as an outsider but as he shows his own magical prowess, they start to teach him about chakra. He then tries to combine the two forms of power, facing challenges along the way like resistance from some in the wizarding world who fear this new form of magic he's bringing in.

It could still be Voldemort. Even with the introduction of the Tensaiga, Voldemort would remain a major threat. He might become even more interested in the Tensaiga once he learns about it, seeing it as a powerful tool to achieve his dark goals.

Well, if Harry Potter discovers chakra, he could potentially gain new magical abilities. He might be able to combine his existing wizardry with chakra - based powers. For example, he could use chakra to enhance his spell - casting speed or strength. Maybe he could even develop new spells that are a fusion of the two magic systems.

It could be a jealous ninja from another village who sees Naruto's infinite chakra as a threat to their own village's power. This ninja might try to steal Naruto's chakra source or find a way to nullify it.

It could be a rogue ninja who is also after the power of the chakra chains. This ninja might see Naruto as a threat and try to eliminate him to get the chains for himself.

Perhaps a long - lost relative of the Potter family who feels they were unjustly excluded from inheriting the manor. This relative could be jealous of Harry's status and the wealth associated with the manor. They might use dark magic to try and claim what they think is rightfully theirs, leading to a battle of magic and loyalty within the Potter family and among Harry's friends.

A new dark wizard or witch could be created specifically for this fanfiction. This character could be interested in using the Huntsman's skills for their own evil purposes. If the Huntsman refuses, they become enemies. This antagonist could have powers related to dark forest magic, something that the Huntsman is familiar with but in a more malevolent form.

Voldemort could still be the main antagonist. Even if Demetri has some sort of connection or change in the fanfiction, Voldemort's overarching evil plans would still be a major threat to both Harry and Demetri, especially if Demetri tries to deviate from the Death Eaters' path.

The minotaur itself could be the main antagonist. It's a powerful and dangerous creature, and if it's been set loose in Hogwarts or is guarding something that Harry needs, it would be a major obstacle for him to overcome.

The main antagonist could be a dark wizard who has made the graveyard his lair. He uses the dark energy from the tombstones and the restless spirits there to power his dark magic. Harry stumbles upon this wizard's activities and has to stop him.