DELETE SOMEONE else grp because of bad comments about me !

You can change your privacy settings and ban people from your account here: http://www.facebook.com/privacy.php

I would also contact Facebook support and ask them to remove the abusive photos and comments by clicking "report group" at the bottom of the group page below the wall posts. 

If you try to hack it, most likely Facebook will ban YOU.  I have heard that they have taken care of it before, there was a man at the University of Kent who was repeatedly harrassed over Facebook and they closed the group when he asked them to.  I seem to remember a similar incident with a high school girl in the U.S. as well.  However you must ask them personally to close it down, if somebody else asks for you they can't do it.  Make sure you ask them yourself and explain why it is bothering you and see what they say.