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.
Sure. In a negan x reader love story, perhaps the reader could be a survivor in the post - apocalyptic world where Negan rules. At first, the reader might be terrified of Negan because of his brutal reputation. But as time passes, Negan starts to notice the reader's unique qualities, like their kindness in a cruel world. He might start to show a softer side only to the reader, gradually leading to a complex love that defies the norms of their world.
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.
Well, it depends on your perspective. But generally, Negan is considered bad in the comic because of his cruel and violent actions towards the main characters.