T'PAU: I can forgive such a display only once. Challenge was given and lawfully accepted. It has begun. Let no one interfere.
(And so the fight begins, first with a trial of brute strength, then a good swing by Spock slices open Kirk's tunic and cuts his chest. It is clear that the first officer will kill his captain, given the chance. When Kirk is down and unarmed, Spock goes in for the final blow.)