Johnny's imperiled reputation rendered him desperate.

He had gone too far to recede, and he went into action with all the energy and skill of a true bruiser.
Tommy was now fully roused, and his blows, which were strictly in self-defense, fell rapidly and heavily on the head of his assailant.
But I am not going to give my young readers the particulars of the fight; and I would not have let Tommy engage in such a scene, were it not to show up Johnny as he was, and finish the portrait of him which I had outlined; to show the difference between the noble, generous, brave, and true-hearted boy, and the little bully, whom all my young friends have seen and despised.
In something less than two minutes, Johnny Grippen, after muttering "foul play," backed out with bloody nose, as completely whipped, and as thoroughly "cowed down," as though he had been fighting with a royal Bengal tiger.

His supremacy was at an end, and there was danger that some other bold fellow might take it into his head to thrash the donkey after the lion's skin had been stripped from his shoulders.
"If you are satisfied now, I'll go about my business," said Tommy, as he gazed with mingled pity and contempt upon his crest-fallen assailant.
"You don't fight fair," grumbled Johnny, who could not account for his defeat in any other way.

"If you're a mind to fight fair, I'll try it again with you some time." "I don't fight for the fun of it.

I only fight when some cowardly bully like you comes at me, and I can't help myself.