There could be a group of purist wizards who believe that magical animals should not be put on display for non - wizards to see. They constantly try to disrupt the zoo's operations, causing trouble for Harry. Harry would need to fight for the right of his zoo to exist and educate these purist wizards about the importance of co - existence between wizards, non - wizards, and magical animals.
Well, perhaps Harry could discover a new magical creature in the zoo. This creature could have the power to make other animals communicate in human languages, leading to all sorts of chaos and hilarity as the animals start voicing their opinions and demands.
Maybe an organization that specializes in using the Sharrigan for malicious purposes. They don't want Naruto to expose their secrets, so they send their Sharrigan - users to hunt him down. This organization could be made up of power - hungry individuals who will stop at nothing to achieve their goals.
Since it's a fanfic that combines Harry Potter and something related to Forks (maybe Twilight), the main characters would likely be Harry from Harry Potter. There might also be characters from the Forks - related story like Bella or Edward if it's a crossover fanfic.
It could be an archaeologist who has been corrupted by the power of an ancient artifact related to the mummy. This archaeologist wants to use the mummy's power for his own gain, like becoming immortal or ruling the world. He would be constantly trying to stop Harry from helping the mummy.
It could be a powerful dark wizard who has also gained some supervillain - like powers. This antagonist might be jealous of Harry's newfound superhero status and wants to destroy him.
Maybe a new character could be the main antagonist. A powerful and mysterious being that Luigi stumbles upon during his escape. This character might have some vendetta against the Mario brothers or just be generally evil and wants to stop Luigi's journey for its own malicious reasons.
It could be a jealous wizard who feels that Harry and his sister are getting too much attention in the wizarding world. This wizard might try to undermine their achievements and even put them in danger.
The main antagonist could be a powerful necromancer who combines the dark arts of Skyrim with some elements of Voldemort - like magic. He could be raising an army of the undead and causing chaos across Skyrim, which Harry has to stop.
It could be Voldemort or one of his Death Eaters. They might be using Harry as a pawn to get to Parvati for some reason, like she has a special power or knowledge that they want.
Maybe an ancient evil spirit that was once bound but is now trying to break free by using the summoner as a conduit. This spirit could be manipulating events from the shadows, causing chaos in the wizarding world to draw the summoner out.