One possible reason could be a misunderstanding. Maybe Merlin did something that Arthur misinterpreted as betrayal or dishonesty. For example, if Merlin was secretly helping an enemy for a greater good that Arthur wasn't aware of at the time.
He might also get angry. Merlin has his own pride and after all he has done for Arthur, being insulted like this would make him furious. He could start yelling back at Arthur, listing all the times he has saved Arthur's life or the kingdom.
A fanfiction that stands out is 'Arthur and Merlin: A Different Path'. This one takes a different turn from the original storyline. It imagines a world where Arthur discovers Merlin's magic much earlier. This changes the whole dynamic between them, and they face different challenges together. There is also 'The Adventures of Merlin and Arthur in the Enchanted Forest'. It's full of exciting quests and the development of their friendship.
One great fanfiction is 'The Once and Future King's Heart'. It beautifully delves into the deep bond between Merlin and Arthur. It shows how their relationship evolves over time, with Merlin's magic playing an important role in protecting Arthur while also creating some interesting conflicts.
One great 'Arthur Pendragon Merlin fanfic' is 'The Once and Future King' -esque story where Merlin's magic is a key factor in Arthur uniting the kingdoms. It shows their deep bond and how Merlin uses his powers to protect Arthur in a very creative way.
A good 'Arthur Pendragon Merlin fanfic' often has a strong portrayal of their friendship. For example, it might show how they support each other through difficult times. Like when Arthur is facing a tough battle, Merlin is there with his magic to help, and vice versa.
The characters themselves are very appealing. Arthur is a noble king - to - be, and Merlin is a powerful wizard in hiding. Their personalities clash and complement each other at the same time. Fans love to explore how they interact and grow together in fanfictions.
One popular one is 'The Once and Future King' fanfic series. In this, Merlin often uses the term'sire' as he plays his role as Arthur's advisor. Another is 'Camelot's Heart' where the relationship between Merlin and Arthur is very much in line with the traditional Arthurian tales, and Merlin's use of'sire' is quite prominent.
Saber from Fate/Stay Night would be an obvious choice. Since she is also related to the Arthurian legend, there could be a lot of interesting interactions between them. They could compare their experiences as king, or even fight side by side against a common enemy.
One great Arthur Pendragon hurt fanfiction is 'The Wounded King' which delves into his emotional turmoil after a major battle. It shows his struggle to regain his strength both physically and mentally.