The demons from Inuyasha's world that resent the idea of a half - human, half - demon having such a powerful combination of abilities could be villains. They might see Naruto as a threat to their existence or way of life and try to eliminate him. Also, there could be ninja who are jealous of Naruto's newfound powers and team up with these demons to take him down.
The Akatsuki could still be major villains, but with a twist. They could be interested in Naruto's connection to Iron Man and his technology. Maybe they want to use it to enhance their own powers or to create a new type of bijuu using Stark's technology. Another option could be a new villain from the Iron Man universe, like Justin Hammer, who finds his way into the Naruto world and decides to use the chaos there to his advantage by creating his own criminal empire using ninja and technology combined.
In the wizarding world, there might be some jealous wizards who don't like Harry's unique combination of powers. They could team up with dark forces, maybe some Death Eaters who are still lurking around, and try to bring Harry down. They might be envious of the attention Harry gets or fear his new - found powers will disrupt the traditional ways of magic.
It could be the classic villains from the original series like All For One. He might be interested in baby Deku's potential quirk. Another could be Shigaraki, who might see baby Deku as either a threat or an opportunity to disrupt the hero world in a new way.
There's a group of villains in the 'Villains Rising Light Novel'. One of the main ones is a woman named Lilith. She is cunning and uses her intelligence to outwit her enemies. Another is a hulking brute named Brutus who uses his physical strength to cause chaos. They all have different motives for their villainy which makes for an interesting dynamic.
I'm not sure specifically as I haven't read the exact novel. But usually, the main villains are those who oppose the protagonist the most. They are often the ones causing the most chaos and problems in the story world.
Salem is also a very popular villain in RWBY fanfiction. Given her status as the main overarching villain in the series, fanfic writers like to expand on her backstory, her motives, and her long - term plans. There could be fanfictions that focus on her interactions with other villains in a more detailed way.
In 'The Lord of the Rings', Frodo is a hero. He undertakes the dangerous journey to destroy the One Ring. Sauron is the main villain, with his desire for domination. Another example is in 'Harry Potter'. Harry is the hero, facing the evil Voldemort. Voldemort is a classic villain, with his pure - blood supremacy ideology and his numerous dark deeds.
πI recommend the following novels to you:
"The Unparalleled Prince's Defiant Wife"
This was an Eastern fantasy romance novel. The main character was a top-notch assassin from the modern era. She transmigrated to the Southern Cloud Nation and became a good-for-nothing ugly girl. However, her strength was that of a genius all-elemental Summoner. She appeared as a black-bellied and evil person, so it was not difficult for her to be a villain. At the same time, there was also a useless prince from the Feng Prince residence who was pestering her endlessly. The entire plot was very subversive. I hope you like this fairy's recommendation. Muah ~π
In " Celebrating Years," there were many villains, including the Eldest Princess, the Second Prince, Fan Xian, Li Yunrui, Xiao En, and the Qing Emperor. Among them, the Eldest Princess, the Second Prince, and the Qing Emperor were considered important villains. The Eldest Princess was the biggest villain in the first season. She pursued higher power and attacked Fan Xian many times with the Crown Prince and the Second Prince. The Qing Emperor was the biggest villain and villain in this play. He was Fan Xian's mother's killer and had conspired with Ye Qingmei when he was a prince.