Heres one of the scripts i have in mind. This is just a summorisation of it.

Don Vincent Corleone, the head of the once most powerful mafia. The year is 1984. Vincents uncle and mentor Michael Corleone still gives him advice though he is retired. Michael is still very somber about the death of his beloved daughter Mary. Five years ago, she was murdered. A man named Donnie Zaza is a close relative of the man Vincent killed named Joey Zaza. The plot stirs when Donnie Zaza completes military training he will use to kill Vincent. Battle breaks out back and forth as Vincent's men hurry fast to find Donnie. But Donnie kills off his men 1 by 1 as he gets closer to Mr. Corleone. Al Neri is retired and living near Michael in Sicily but Zaza captures him and threatens to kill him. Will Vincent find a way to save Neri? As time runs out and Donnie clips one guy after another to get to Vincent and finish his vendetta...