A Bullet for Sandoval (1969)

After his girlfriend dies in childbirth, Confederate deserter John Warner travels to Mexico, where the woman's father, Don Pedro Sandoval, grudgingly hands over his child. But with no locals willing to provide milk, the baby dies. Rounding up a group of rebels, Warner goes on a rampage through northern Mexico, with the ultimate goal of taking down Sandoval in this gritty Western.

Unfortunately the movie A Bullet for Sandoval is not yet available on HBO Max.