Ed Begley in '12 Angry Men' (1957).

Juror 10 is the secondary antagonist in the 1957 film, Twelve Angry Men. His motive for voting the defendant guilty is because he had a prejudice against the people from the boy's neighborhood, which are called 'Slums'. Throughout the film, he keeps throwing his prejudice around the Juror room so the others can vote guilty. It isn't until giving a tirade about the faults of Slums that he gives in when the Jurors give him the cold shoulder and he lets the Jurors vote whatever way the please.