Climactic Battle

By this point in the film, the fate of something (typically the world) is is usually on the line.  The hero has just gained extra motivation to go and kick some *rse.  The villain has often retreated to his final base, with the last of his elite henchmen to keep him safe.  That, or the hero has already dispatched of the henchmen and is staring the villain down, setting the stage for an epic final showdown.  This is what the film has spent its entire time building up to and the result of the final battle wraps up the main story and leaves the audience feeling satisfied.