Eragon would likely be one of the most powerful. His bond with Saphira gives him access to powerful dragon - based magic. He can also use the ancient language to perform various spells. In the power - hungry world of Game of Thrones, his abilities would make him a force to be reckoned with.
Arya Stark could potentially be very powerful if she had some of the skills from the Inheritance Cycle. Imagine if she could use the ancient language to control her enemies or had the physical abilities of an elf. She could use these new skills to take her revenge and manipulate the political situation in Westeros even more effectively.
Perhaps the Urgals from the Inheritance Cycle invade Westeros. Their brute strength and different culture would disrupt the balance of power. The different houses in Westeros would have to put aside their differences to fight this new threat. And a character like Jon Snow could learn about the Urgals' way of fighting and use that knowledge to his advantage in future battles.
The 'Game of Thrones' cycle in the cartoon often emphasizes the key plot points and characters, but with a visual style adapted for animation.
It's likely that Percy Jackson himself would be very powerful. His ability to control water gives him a huge advantage, especially in a world like Westeros where there are many bodies of water. He could drown his enemies or use water to deflect attacks. However, Daenerys with her dragons would also be a formidable opponent. Her dragons could breathe fire and fly, which is hard to combat.
In 'Game of Thrones Godlike Fanfic', characters like Bran Stark might be among the most powerful if his warging abilities are taken to a god - like level. He could potentially possess any living being or even control multiple minds at once. Also, the Night King could be made even more formidable if given additional powers. For example, if he had the power to not only raise the dead but also to control the elements, like creating blizzards at will, he would be a terrifying and very powerful force in the story.
Sauron, if he were in his full power, would be terrifying. His ability to control minds and his dark magic could potentially subdue many of the 'Game of Thrones' characters. But he might underestimate the political cunning and the will of some of the more tenacious Westeros leaders, which could lead to his downfall in this fictional battle.
Klaus Mikaelson might also be considered the most powerful. His hybrid status gives him super strength, speed, and the ability to compel others. In the world of Game of Thrones, he could easily use his compulsion on many of the characters to get what he wants. He's also very difficult to kill, which would give him an edge over most characters from Game of Thrones.
It could be Jon Snow. If he has a Stand in the fanfiction, combined with his already proven leadership skills and combat abilities, he would be a force to be reckoned with. His ability to come back from the dead might also be related to his Stand powers in some way, making him even more formidable.
Well, it could also be argued that Daenerys Targaryen might be very powerful in such a fanfic. She has her dragons, which are extremely powerful weapons. If she were to enter Narnia, she could potentially use her dragons to gain a stronghold. However, she would still be no match for Aslan in terms of pure power and divine essence.
It might be Ruby. Her speed and her scythe skills could make her a formidable opponent in the battlefields of Westeros. She could quickly move around and take out enemies before they even realize what's happening.
Arya is an interesting character to write about. She has a complex personality and a lot of responsibilities. Fanfic writers can explore her feelings towards the humans more, especially considering her elven heritage. Also, Murtagh. His tortured past and his complex relationship with Eragon provide a rich ground for storytelling. Writers can explore what could have been if he had made different choices or if he had been given more support early on.