See here http://support.chess.com/Knowledgebase/Article/View/122/0/what-should-i-do-if-another-member-is-rude-or-abusive. If serious enough you are invited to submit an Abuse Report.
See the post by staff member kohai about players walking away without resigning http://www.chess.com/forum/view/chess-players/childish-behaviour . "We are working on something (coming soon) that will hopefully alleviate this"
During the following game.. the member rajeshksm made a mistake and abused me foully by calling me a "mother fckr" and on his move made me wait for the rest of the game.. it was a 10 minute game and I need help to deal with people with this sort of callibre... Please help
this was the game :