In The walking Dead comics, there's no explicitly mentioned character who is immune. The focus is more on survival and the challenges faced by the group rather than immunity.
Since it's an OC fanfiction, the main character is likely the Original Character who is immune. But there could also be other characters from the Walking Dead universe that interact with the OC. Maybe Daryl, who is known for his survival skills, could be involved. He might be initially skeptical of the OC's immunity but later come to rely on it.
As of the latest comic issues, Daryl is alive. The storylines have managed to keep him in the thick of the action without killing him off.
No, Judith isn't dead in the comics as of the latest issues I know.
Michonne does die in the comics. The circumstances surrounding her death were quite dramatic and had a significant impact on the story's progression. It happened during a major conflict with other characters.
Yes, Negan dies in The Walking Dead comics.
Yes, Carl dies in the Walking Dead comics.
Yes, Glenn dies in the comics. It's a tragic moment for fans.
Yes, Rosita is dead in the comics.
Yes, Negan dies in the Walking Dead comics.
Yes, Alpha is dead in the Walking Dead comics.