Death Smiles on a Murderer (1973)

Greta is a beautiful young woman abused by her brother Franz and left to die in childbirth by her illicit lover, the aristocrat Dr. von Ravensbrück. Bereft with grief, Franz reanimates his dead sister using a formula engraved on an ancient Incan medallion. Greta then returns as an undead avenging angel, reaping revenge on the Ravensbrück family and her manically possessive brother.