Set in New York City in 1981, the film's stars say it has the look and feel of a gangster movie but it's a lot more than that.
"It's just not the cliché you expect it to be," Isaac said. "It's actually a reaction to that kind of thing."
Isaac -- who dropped his surname Hernandez when he became an actor -- says his character defies stereotypes.
"You don't usually see a character of Latin descent portrayed this way. He is not going to be the gangster, he is not going to use violence; he is going to succeed by taking the smart, long view."
Co-star Jessica Chastain says she lobbied hard for Isaac to get the part.
"I was feeling very impassioned and I wrote this email about how much I believed in Oscar," Chastain said. "He is Genius."
The actors go way back; they studied together at Julliard.
"A Most Violent Year" opens in limited release on Wednesday, Dec. 31.