Clash of the Titans (1981)

Perseus (Harry Hamlin) is the favored son of the god Zeus (Sir Laurence Olivier), but he has unwittingly ticked off the sea goddess Thetis (Dame Maggie Smith). Just to make things worse, Perseus falls in love with the lovely Princess Andromeda (Judi Bowker), who used to be engaged to Thetis' son, Calibos (Neil McCarthy). Soon Perseus is off on one quest after another, with Zeus helping, Thetis hindering, and lots of innocent bystanders getting stabbed, drowned, and squished.