Well, it's hard to name the 'best' as it depends on personal taste. But some authors who are quite popular in the Carl and Negan fanfic community are those who really capture the complex relationship between the two characters. One such author might be someone who goes by the pen name 'WalkingDeadFan123'. Their stories often explore the psychological aspects of Carl and Negan's interactions in great detail.
Negan might protect Carl out of a sense of respect. Carl has shown himself to be a strong and determined character, and Negan could admire those qualities.
One interesting Carl and Negan fanfic could be about Carl trying to understand Negan's motives. Maybe Carl starts to see that Negan isn't just a one - dimensional villain. For example, in some fanfics, Carl might discover that Negan has a past that led him to be so ruthless in the present. He could also find common ground with Negan, like their will to survive in a harsh world.
One good story could be where Negan realizes Carl's potential and decides to protect him from other threats in the post - apocalyptic world. He might see Carl as a symbol of hope or a reminder of his own humanity.
Well, Negan first appears in the series as a major antagonist. He has a very distinct personality. He's confident, often to the point of being cocky. His group, the Saviors, would extort other communities for resources. He uses fear as a tool to control those around him. His actions have a huge impact on the other characters in the show, like Rick and his group.
There's not enough information to know exactly who Carl is. He could be a family member, like a grandfather or father, sharing a beloved Christmas story. Or perhaps he's a local storyteller in a community.
Rick is a very likely character to interact with Negan in hurt Negan fanfiction. Their relationship has been a central part of the original story, and in fanfiction, their interactions could be further explored, especially if Negan is in a 'hurt' state. Another character could be Carl. Carl had his own complex relationship with Negan, and in fanfiction, their dynamic could be developed in new ways.