After prompting from a couple of users to make my comment an answer
The goal is not merely to force Worf to yield, but to break him both physically and especially psychologically. It is not enough for the Jem'Haddar in this context to simply execute, else they would have already done that. This cage match is to demonstrate utter superiority and dominance, as well as to gauge what the Klingons as a people are capable of.
IKAT'IKA: Today, we train against a worthy adversary. Observe,
analyse, remember. Soon we will face his people in combat. The lessons
you learn here will ensure victory. Victory is life.
Remember too that Worf wins five straight victories against other Jem'Hadar prior to fighting Ikat'ika:
DEYOS: You fight because that is what you were designed to do. All
that motivates him is some barbaric sense of honour.
IKAT'IKA: And that is something you will never understand. Prepare
yourself. I've found you a worthy opponent.
That Worf will not yield, that he will keep getting up again, and again, and again, until he is outright killed may prove the tactical superiority of the Jem Had'dar, but not the mental superiority. Even Martok says that Worf has more than met the challenge and is able to honorably 'quit',
MARTOK: Worf, honour has been satisfied. Stay down.
IKAT'IKA: Enough, Klingon. You have proven your worth.
MARTOK: Worf, you heard him. Enough.
WORF: I will not yield.
Worf does not mind losing to a worthy opponent in honorable combat ("Today is a good day to die"), but he will never surrender or yield. Worf will not be broken. He will not be intimidated. When First realizes this, the true battle is over. Worf has proven himself as a warrior equal to the best of the Jem'Hadar, not in combat necessarily (because Ikat'ika does state that he could kill Worf) but because ultimately, they share the same core ethos: victory is life, defeat is death.
And, as Deyos demonstrates: defeat is indeed death for Ikat'ika.
IKAT'IKA: I yield. I cannot defeat this Klingon. All I can do is kill
him, and that no longer holds my interest.
DEYOS: Shoot them both.
If, as Ikat'ika states at the begining of the combat, that the purpose is to train and learn, then Deyos provides the final and ultimate lesson to the rest of the Jem'Hadar standing around watching when he executes Ikat'ika for showing mercy or solidarity with another warrior. Recall Ikat'ika's words:
"The lessons you learn here will ensure victory. Victory is life"