Run Home Slow (1965)

"Four frightened people... bound together - torn apart by their own evil!"

Rugged cowgirl, Nell Hagen sets out to retaliate for the hanging of her father Judd, who ruled their valley with an iron fist before the natives revolted. She is accompanied by her brothers, Ritt and Kirby, a hump-backed half-wit, and their sensuous cousin Julie Ann. The family then robs a bank, kills two tellers, enacts their revenge before heading for the border where their own family drama gets really mean and nasty.