Thomas Mitchell
The '1939' triplet:
Stagecoach (1939) (Best Supporting Actor),
GONE WITH THE WIND (1939),
Mr. Smith Goes to Washington (1939)
Here is a list of other actors' "3-set of major performances from the same year"; which one do you think had the most impressive year?
After voting, you may discuss the list here
Best Picture Nominee BEST PICTURE WINNER (Oscar nomination) (Oscar win)
1968 was an interesting year too, but '71 takes the edge with the first 'Dirty Harry' movie and Clint's directorial debut.
1964 was his breakthrough year, he was 50 and two successful movies propelled him at the Top of French box office for the rest of his career.