|Nicholas and Alexandra (1971) [Tatiana]: Executed (along with the rest of the royal family) by a firing squad of Bolsheviks in the basement. We only see the Bolsheviks firing repeatedly, followed by a shot of the bloody, bullet-riddled wall; the bodies are not shown.
Henry VIII and His Six Wives (1972) [Catherine Howard]: Executed (off-screen) by beheading; the scene ends just as she kneels down before the chopping block. (Thanks to Johan)
Royal Mounted Police (Giubbe rosse; Cormack of the Mounties; Red Coat) (1974) [Elizabeth Cormack]: Dies (off-screen) of unspecified causes, approximately ten years before the movie begins; she only appears in flashbacks, and Fabio Testi mentions in the dialogue that she died when their son was two years old. (Thanks to Johan)
Four of the Apocalypse (I Quattro dell'apocalisse; Four Gunmen of the Apocalypse) (1975) [Emanuela 'Bunny' O'Neill]: Dies shortly after childbirth, with Fabio Testi at her bedside.
Voyage of the Damned (1976) [Anna Rosen]: Commits suicide, along with Malcolm McDowell, by drinking poisoned wine. Their bodies are shown afterwards when Max von Sydow enters Malcom's cabin and discovers them.