The Ballad of the Ferocious One (1971)

Deeply hurt by his wife's adultery, a man leaves her and his son to live high up alone in the mountains of Montenegro. Many years later, the war breaks out and the two enemy factions must cross the very mountain. One of them seeks the man's help to find a path through the snow. Later that day, he finds out that one of the other side's members is no other than his son.

Unfortunately the movie The Ballad of the Ferocious One is not yet available on HBO Max.