How did I not know about this movie?
"8. True Confessions (1981)
Duvall and Robert De Niro get the best out of each other in Ulu Grosbard’s intelligent movie, co-written by Joan Didion and John Gregory Dunne, and based on Dunne’s novel inspired by the Black Dahlia case. Duvall plays a tough LAPD detective in the 40s, haunted by a corrupt past that he has put behind him. His younger brother is De Niro’s idealistic young catholic priest, who receives donations from a somewhat shady businessman. A gruesome murder brings the two into a mutually anguished confrontation."
https://www.theguardian.com/film/2022/dec/08/robert-duvalls-20-best-performances-ranked