an exceptional achievement by an artist, author, or the like, that is unlikely to be equaled by that person or anyone else; stroke of genius

Herman Melville's Moby Dick was a tour de force.

a particularly adroit maneuver or technique in handling a difficult situation

The way the president got his bill through the Senate was a tour de force.

a feat requiring unusual strength, skill, or ingenuity.

noun

accomplishment , achievement , attainment , chef-d\'oeuvre , conquest , deed , exploit , feat , feat of strength , grand achievement , great achievement , magnum opus , master stroke , masterpiece , masterwork , performance , piece de resistance , stroke of genius , success , triumph , victory , gest , masterstroke , stunt