fix-it

noun[before a noun]1

1. •
   (slang) A fanfic which undoes or changes an element of canon viewed as unfavourable, e.g. a death, break-up, or betrayal.

   • I've written fix-it fic myself: unhappy with the sad ending in the final season of BBC's Merlin, I rewrote the entire fifth season; […] — 2017