Greedy Appetite (1977)

After Tini catches her boyfriend Narno trying to seduce her sister Tina and ends their relationship, she mysteriously dies from a snakebite. Narno's mother then visits a shaman to place a curse on one of Tina's potential suitors. As all of that is going on, a mysterious murderer is lurking around bumping off other members of both Tina and Narno's families.