I've not seen THE GREAT SANTINI, but I believe there's a scene where the Robert Duvall character is very nasty to his son, bouncing a basketball against his head while hectoring him, something like that.

And this person commented they were very lucky to get a major actor like Duvall to portray that character, and it was brave of him, since film stars in general never want to do unsympathetic characters on the grounds that the public will stop liking them.

Something to bear in mind when writing major characters.

Martin, if you watch that scene I've embedded in the OP, that's the one you're talking about. And you're right: it's a hard scene to watch as Meechum (the father) is just horrible, taking out his hurt on his son. But a gripping moment.