Use the link to delete your account. Otherwise, try this link: http://www.xing.com/app/help?op=show;id=185
URLS:
http://www.xing.com
http://www.xing.com/app/user?op=cancel
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.