You can start by saying something like....
Dear Sir,
I sincerely apologize for kicking you in the groin region, I realize I have no respect and think something like this is okay. I am writing you this letter because a judge is forcing me too. I got the majority of this letter from yahoo answers because, I am not really sorry I am just fulfilling a part of my punishment. I would kick you in the balls again if i knew I could get away with it. Next time why don't you just wear a cup.
Peace