Who could be potential villains in 'Kairi Prisoner of Darkness' fanfiction?

A great plot could involve Kairi finding an unexpected ally within the prison of darkness. This ally could be someone who was once an enemy but now has a common goal with her. She could also start to understand the true nature of the darkness and find a way to use it to her advantage, rather than being completely overpowered by it.

A powerful wizard who wants to use the 'lady of darkness' powers for his own evil gains could be an antagonist. He might try to manipulate her into doing his bidding.

Many of the powerful noble houses would be his enemies. For example, the Lannisters, who are already in a struggle for power. They would not want to share or lose their power to the Prince of Darkness. And the Tyrells, who are also politically astute and would view the Prince as a threat to their influence and the stability of the Seven Kingdoms.

The Lizard could be turned into a more supernatural villain. Maybe he gets possessed by an ancient spirit that makes him not only stronger but also able to control other reptiles with dark magic. This would pose a huge threat to Spider - Man as he has to deal with the Lizard's new powers on top of his already dangerous physical abilities.

There could be a secret organization that believes the chosen one's power will disrupt the balance they have carefully maintained in the Pokemon world. They would be villains as they try to eliminate the chosen one and the Pokemon helping them, thinking they are doing what's best for the world but in a very wrong way.

In a crossover with the Marvel universe, Thanos could be a formidable villain. His desire to collect the Infinity Stones and his power would pose a huge threat to the Power Rangers SPD. The Rangers would have to team up with the Avengers to stand a chance against him.

There are several potential villains. In the Naruto world, Orochimaru would surely be interested in Naruto's new Ultraman powers. He might try to experiment on Naruto to figure out how to obtain those powers for himself. From the Ultraman world, the Alien Mefilas could be a villain. They are known for their cunning and would likely see Naruto as a target. Additionally, some of the rogue ninja in the Naruto world who are power - hungry might team up with the Ultraman villains. They could form an alliance to take over both worlds, seeing Naruto's unique powers as the key to their success.

Nico di Angelo could be a great ally. Since he has his own connection to the Underworld, he might understand Percy's new situation better. Another could be Thalia, as she's always been a strong and loyal friend. She would likely stand by Percy despite his new dark powers. Also, Grover could be an ally. His empathy and loyalty would make him support Percy no matter what.

A really good villain could be an ancient Titan who has been awakened from his slumber. He's angry at the gods and wants to take revenge by destroying their favorite demigods, Percy and Annabeth. He has the power to manipulate earth and fire, which makes him a formidable foe.

A cyborg assassin could be a new villain. This villain could have been created by a shadowy organization to take out Spiderman 2099. With enhanced strength, speed, and the ability to hack into any digital system in the city.