In the flashback sequence of The Last Jedi, have Luke straight up murder Kylo Ren in cold blood. Then, give no explanation for why Kylo is still alive in the present.
Essentially what happened in the “movie”
You mean to tell me Luke actually sliced off Kylo Ren’s head in the flashback all this time? Damn, I must be losing my memory.
Jack Napier lives in a society where that happened.