Maybe "Helpmetoo" could have put it a little more subtely, but in essence, he/she is only expressing what most people are thinking.
It sounds like you and your "mates" carried out a cowardly attack on another person, you admit to kicking and punching him as he tried to get away, then your pals joined in by kicking him as well.
Thugs like yourself, are ruining society with mindless violence, god only knows how far you would have been prepared to go if this lad had done more than "make your sister cry".
You should be taught a severe lesson and should receive the maximum sentence available, you have been advised to plead guilty in the hope this will reduce your sentence, I sincerely hope this fails and you are put away for a couple of years, at least the streets will be free of just one drunken thug who believes he has the right to take the law into his own hands, and in the most cowardly way possible i.e. like a pack of dogs.
Dont like this answer? Then think for a second next time you put the boot in.
And think about how your parents are going to feel when you're inside, and also about what could have happened, A few mindless kicks could have ended this persons life, for what, a couple of tears.