The Octagon

When a rich woman realizes that she is the target of an assassination by a ruthless band of Asian revolutionaries, she asks a revered karate expert to wipe them out for her. The black belt accepts the assignment after he learns that his former classmate (and hated rival) is the ringleader of the killers. The martial arts master pursues his enemies to the octagonal-shaped room where they spar -- and soon he's deep in blood and violence, fighting for his life. (official distributor synopsis)