Lucio Fulci - Le colt cantarono la morte e fu… tempo di massacro AKA Massacre Time (1966)

A wealthy land baron’s sadistic son has taken to abusing the local citizenry with his bullwhip in perverse, evil games.
Prospector Franco Nero returns home to help his alcoholic half-brother and finds a maniacal, bullwhip-wielding tyrant controlling the land and Nero’s sibling.
Nero joins forces with his kin to try to beat the sadistic creep and his followers.