The Devil's Rain. Contains cultists that melt into puddles of wax upon death, Ernest Borgnine as a Satanic priest/demon, and William Shatner whose character tries to become a Capt. Kirk-esque hero at first, only to become the movie's ultimate tragic sacrificial lamb. One of the spookiest films I've seen IMO, but wasn't that the norm for 70s B-horror movies?
Scanners is a close second, based on the gory final telekinetic battle between Vale and Revok in which Vale gets totally mutilated but still wins by taking over Revok's body...
Tim (aka the Slipperman)