Here's a few who should have been nominated in my opinion
Anthony Perkins for Psycho
Robert Mitchum for Night of the Hunter.
Ingrid Bergman for Casablanca
Bibi Andersson and Liv Ullmann for Persona
John Cazale for Dog Day Afternoon/ Godfather part 2
Scarlett Johansson for Lost in Translation
Malcolm McDowell for A Clockwork Orange
Henry Fonda for The Grapes of Wrath
Maggie Cheung for In the Mood for Love
Eli Wallach for The Good, the Bad, and the Ugly
R. Lee Ermey for Full Metal Jacket
Sidney Poitier for In the Heat of the Night
Toshiro Mifune for Seven Samurai
Anthony Perkins for Psycho
Robert Mitchum for Night of the Hunter.
Ingrid Bergman for Casablanca
Bibi Andersson and Liv Ullmann for Persona
John Cazale for Dog Day Afternoon/ Godfather part 2
Scarlett Johansson for Lost in Translation
Malcolm McDowell for A Clockwork Orange
Henry Fonda for The Grapes of Wrath
Maggie Cheung for In the Mood for Love
Eli Wallach for The Good, the Bad, and the Ugly
R. Lee Ermey for Full Metal Jacket
Sidney Poitier for In the Heat of the Night
Toshiro Mifune for Seven Samurai