I was thinking of his film The Apostle a few days ago. Amazing movie. No studio would touch the project so Duvall financed, directed and starred in it himself.
I loved that film. He brought so much to the role.
It actually attempted to portray Southern Pentecostals genuinely (though over-emphasizing the Holy Spirit) and culture overall positively and used many actual members as actors while even the furniture store owner was not an actor, and some footage was off-script. And police were shown as respectfully waiting until after pastor "Sonny" finished preaching. And while "Sonny" certainly was a problem, yet his wife was the worse offender.