Bad dogs: The Hounds of Zaroff (1932) hunted humans; The Hound of the Baskervilles did likewise; pack attacks enlivened Dogs (1976) and Moonraker (1979). Gregory Peck was savaged in The Omen (1976) and The Boys from Brazil (1978). Zoltan, Hound of Dracula (1979) drank blood.
Sentimental hounds: Old Yeller (1957) died while children wept; Greyfriars Bobby (1961) guarded his owner's grave; My Life as a Dog (1985) directed by Lasse (geddit?) Hallstrom.
Neurotic dogs: Matisse refused to eat in Down and Out in Beverly Hills (1986); White Dog (1982) attacked black people. He was de-programmed.