Act of Vengeance (1974)

Act of Vengeance (1974) 

aka

Rape Squad

City Monster

The plot revolves around a hockey-masked serial-rapist who spouts of silly one-liners and makes his victims sing "Jingle Bells" as he bones them. A group of victims that all meet up to try to ID the rapist at a police line-up decide that the cops aren't taking a serious enough interest in their case, and decide to start a women's group to support and help rape victims. Along the way, hockey-mask surveils the women and in their attempts to try to smoke him out - Mr. Rapist devises his own plan to trap the "Rape Squad" so he can have a final bit of fun with them all collectively... (IMDB  EVOL666)