It sounds like a grand old time, all right. First, there’s that title. Killer Nun. Adjective noun, conveying irony and promising subversion. Then there’s the cast. How can you not want to see Anita Ekberg star with Joe Dallesandro in a killer-nun movie? And the premise (dope-addled sister at a convent hospital starts abusing patients) does not disappoint–imagine a season of “Nurse Jackie” under showrunners Dario Argento and Abel Ferrara. Yet somehow, director Giulio Berruti blows it: A derivative slasher pic and an only mildly lascivious sex film, Killer Nun is the sort of sleepy-eyed misfire that could give nunsploitation a bad name.