More on turning enemies into friends

Mostly, I enjoyed the Back to the Future movies...except for the last one. That's the "Wild West" adventure, where our stalwart hero journeys back in time and encounters the ancestor of his nemesis, Biff. We know that Biff has been raised by a viciously critical grandmother, and said ancestor is obviously the reason for her nastiness. He's not only physically disgusting, but a bully and a coward, apparently devoid of any redeeming virtues. In this family, each generation perpetuates the abuse heaped upon it by the one before.