Maybe a mysterious outsider who has a grudge against Naruto's family and decides to make them forget about Naruto as part of their revenge plan. This villain could be someone from a rival clan or a rogue ninja with a vendetta. They might use dark jutsu to manipulate the family's memories and isolate Naruto.
There's a possibility that the main villain is an internal conflict within Naruto himself. His feelings of being forgotten could manifest as a sort of 'inner demon' that tries to stop him from reconnecting with his family. This would be an interesting take as it shows how Naruto's own insecurities can be his biggest enemy in the context of the fanfic.
It could be a jealous relative who wants Naruto out of the picture so they can have more attention or power within the family.
It could be a rogue ninja who has a grudge against Naruto. This ninja might have developed a special jutsu that can manipulate memories. He uses it on Naruto's friends to make them forget Naruto, hoping to isolate and break Naruto's spirit.
Maybe the main antagonist is a member of Naruto's own family who is power - hungry. This family member sees Naruto's growth to the Jounin level as a threat to their own position within the family. So, they manipulate the rest of the family into forgetting Naruto and excluding him from the family unit. They would stop at nothing to keep Naruto away and maintain their own power and influence.
It could be a new character, a powerful dark wizard who wants to use the combined power of Naruto's chakra and Pikachu's electricity for his own evil purposes. He creates all sorts of dark creatures and sends them after Naruto and Pikachu to try and capture them. He's very cunning and has a lot of minions to do his bidding.
The 'naruto forgotten by family fanfic' might explore Naruto's emotional journey as he deals with being forgotten. He could start to question his identity and his place in the family. As he tries to get his family's attention back, he may discover secrets about his family that were previously hidden. He might also face challenges from those who don't want his family to remember him, and he would have to fight against them while also trying to re - establish his connection with his family.
It could be a rogue ninja who is jealous of Naruto and Sakura's happy family. This ninja might have some grudge against Naruto from the past, and now that Naruto has a family, he wants to disrupt their peace.
A powerful demon named Malice could be the main villain. He has the ability to absorb both chakra and ki, making him a formidable foe for Naruto and Goku. He has a dark plan to destroy both the Naruto universe and the Dragonball Super universe and create his own realm of chaos.
It could be Orochimaru. He has always been interested in dark and forbidden jutsus. He might have found a way to create the 'mob of the dead' situation to test his new powers or to capture Naruto for his own purposes. He could use his snake - like minions along with the undead to create chaos.
Maybe a rogue ninja who has learned about modern technology and uses it to his advantage. He could be stealing valuable ninja artifacts and using modern gadgets to cover his tracks. He's smart like the villains in Case Closed, but also has the power of a ninja. He would be a difficult opponent for Naruto and Conan to face as he can blend the two different worlds' tactics.
A powerful dark wizard could be the main villain. He could be jealous of the clone's unique powers and want to steal them for himself. He might use dark magic to try and corrupt the clone or simply try to destroy it to prevent it from becoming too powerful.
Perhaps a powerful and unknown shinobi from a far - off land. This shinobi has heard of Team 7's reputation and sees them as a threat to his plans of world domination. He uses his unique and mysterious jutsu to challenge Team 7 at every turn, and they have to figure out his motives and weaknesses to stop him.