Superargo and the Faceless Giants

Superargo and the Faceless Giants (original title L'invincibile Superman) is a 1968 Italian-Spanish superhero movie starring Giovanni Cianfriglia as Superargo, a masked wrestler and superhero (in the mold of Mexico's Santo) who battles a mad scientist who is turning athletes into deadly, mindless robots. It was one of several movies featuring Superargo.

Plot Summary
Superargo has retired from the wrestling ring and has decided to devote himself to improving his crime-fighting skills, teaming up with an Eastern mystic named Kamir (Aldo Sambrell). He soon gets an opportunity to out his skills to use when he is approached by the government for help; a strange army of "faceless" humanoids (they really just have stocking pulled over their faces) have been committing crimes and kidnapping athletes.

Superargo investigates. He attempts to capture a giant by using Claire (Luisa Baratto), the sister of a kidnapped man, as bait, but this only results in Claire getting kidnapped and Superargo getting a lot of bruises. His next attempt, staging a wrestling match and tricking the giants into kidnapping his double, is more successful, and Superargo is able to capture one of the robots. He learns that the robots are actually the kidnapped athletes, who have been turned into mindless automatons by the evil Professor Wond (Guy Madison). Meanwhile, the Professor uses a machine to brainwash Claire into killing Superargo.