|Shock (Beyond the Door 2) (1977) [Dora]: Slits her own throat with a utility knife in the basement; it's ambiguous whether she's being controlled by the ghost of her husband (Ivan Rassimov) or whether she's just gone insane.
Inferno (1980) [Countess Elise Van Adler]: Stabbed to death by a shadowy assailant after being clawed and bitten by a swarm of cats. We only see a close-up of the knife plunging downwards.
The Life of Verdi (Verdi) (1982) [Margherita Barezzi]: Dies (off-screen) of a fever; we learn of her death from the narration, and her body is shown afterwards with her husband (Ronald Pickup) by her bedside. (Thanks to Johan)
Phenomena (Creepers) (1985) [Mrs. Bruckner]: Slashed to death with a straight razor by Donald Pleasence's pet chimpanzee.
Opera (Terror at the Opera) (1987) [Mira]: Shot in the eye by Urbano Barbarini while looking through the peephole of the door.
Scarlet Diva (2000) [Anna's Mother]: Dies (off-screen) of a drug overdose in her bedroom; her body is shown afterwards when her children (Gloria Pirrocco and Leonardo Servadio) discover her. (Thanks to Becca)
Mother of Tears (La Terza madre; Mother of Tears: The Third Mother) (2007) [Elisa Mandy]: Killed (off-screen) by the cultists, several years before the story begins; she appears as a ghost to her daughter (Asia Argento) after Valeria Cavalli contacts Daria's spirit.