Who could be the main antagonist in a 'Lord of the Cosmos Coiling Dragon' fanfiction?

Well, you could have a story where the coiling dragon is in danger. Some dark force from another part of the cosmos is trying to capture it and use its power for evil. The main character, who might be a young hero or heroine, has to find a way to save the dragon. This could involve them having to master new powers, make alliances with strange creatures, and journey through uncharted parts of the cosmos. Along the way, they learn about the true nature of the lord of the cosmos and how the coiling dragon fits into the grand scheme of things.

A long - forgotten evil entity that was once bound by the Greengrass family magic could be awakened. This entity sees Harry as a key to breaking free completely and causing chaos in the wizarding world. It would try to manipulate Harry and turn him against the Greengrass family or use their combined power for its own evil purposes.

It could be another powerful dark wizard who sees the relationship between Sabrina and the Dark Lord as a threat to his own power and plans.

A jealous rival who also wants to be known as the dragon master. This person would try to undermine Ash at every turn, spreading false rumors about him and trying to steal his dragon - taming techniques.

Another possibility is a corrupted dragon spirit that has been awakened due to the mixing of the two worlds. This spirit could be spreading chaos and trying to destroy both the ninja world and the dragon world. Naruto would have to figure out a way to stop it, as it has powers that are beyond what he has faced before.

Maybe an ancient dragon that has been awakened from its slumber and views Natsu as an intruder in the dragon world. Since Natsu is a new - made dragon, this old dragon might try to drive him out or even harm him.

A powerful dark wizard could be the main antagonist. He might be jealous of the dragon rider's powers and the bond with the dragon, and wants to break that bond and steal the rider's powers for himself.

It could be a dragon hunter who sees Hiccup in his dragon form and wants to capture him for study or to use his unique abilities for evil purposes.

It could be a powerful dragon hunter. This person would see Naruto's dragon as a prize to be captured or killed. They might have a personal vendetta against dragon riders in general.

Maybe an evil Namekian. Namekians have unique powers, and an evil one could use his abilities to manipulate the life energy in a way that creates zombies. He might be jealous of the Saiyans' power and wants to use the zombies to wipe them out. He could also be in cahoots with some of the other villains from the Dragon Ball series, like Cell. The heroes would have to not only fight the zombies but also figure out this Namekian's motives and how to stop him.