Elf Naruto Fanfiction: Who could be the main antagonist?

Perhaps a dark elf from the elf OC's world who has turned bad. This dark elf could be jealous of the elf OC's connection with Naruto and the Naruto world. So, he follows the elf OC to the Naruto world and tries to disrupt their friendship and cause chaos. He might have some dark magic that is a threat to both Naruto and his friends as well as the elf OC.

Maybe an ancient and evil tailed beast that has been sealed away for a long time. It senses the presence of the female elf, who has some sort of energy that could break its seal. It manipulates other villains in the Naruto world to try and capture the elf. Naruto has to not only protect the elf but also find a way to stop this tailed beast from being unleashed.

It could be Voldemort. He might see turning Harry into an elf as a way to weaken him. Since elves are generally seen as lower in the wizarding hierarchy, Harry in this form would be less of a threat to Voldemort in the eyes of many wizards.

It could be someone from the Naruto universe who doesn't like Naruto's newfound fascination with Aku. For example, Danzo might see Naruto's interest in Aku as a threat to the stability of the village and try to stop Naruto from further exploring Aku - related things. So, Danzo could be the main antagonist in this case.

Maybe a new character could be introduced as the main antagonist. This character could be from a hidden village that has been secretly observing Naruto's growth. They realize his potential as a weapon and plan to steal his power or use him to start a war against other villages.

Krampus himself could be the main antagonist. Since he is a figure known for punishing the naughty, his actions in the Naruto world might be seen as unjust. He could be going after ninjas without really understanding their motives, causing a lot of trouble for the main characters.

It could be a rogue ninja who also has somehow acquired bankai - like powers. This antagonist might be jealous of Naruto's newfound abilities and wants to prove that he is the stronger one. So he starts causing chaos in the ninja world, challenging Naruto at every turn.

It could be a rogue ninja who wants to disrupt Naruto's business to gain power. Maybe he's jealous of Naruto's success and popularity in the business world. He could try to steal Naruto's business secrets or sabotage his operations.

It could be a rogue Kumo ninja who is jealous of Naruto's power and wants to prove himself by defeating Naruto. This ninja might have some dark secrets and a grudge against Kumo as well.

It could be Orochimaru. He's always been interested in immortality and reanimation techniques. Maybe he reanimates Naruto for some evil purpose, like using Naruto's power to take over the ninja world.