Behold the Man by Michael Moorcock tells the story of a fundamentalist Christian who travels back in time to meet Jesus, finds him unsatisfactory and too Jewish, so kills him and takes his place creating "proper" Christianity as God wants it to be. Even going so far as to have himself crucified. In the mean time the real Jesus has recovered from his injuries and and amnesia and finds himself the object of adoration and a messiahship he finds blasphemous, so runs away.
This novel is a masterpiece of allegorical fiction about just how people become obcessed with their own idea of how religion should be, having no respect for the the truth or of the origin.
There was an attempt to make a TV Twilight Zone episode of the story, but it was blocked until they changed the lead from Jesus to Elvis Presley. (the writing credit goes to a young George R.R. Martin and is called “The Once and Future King,” but is clearly a rewrite post dating Moorecock by 17 years.)