There’s no way to delete your account manually. Quite strange for this privacy related web service!
From their page: You may cancel your membership by contacting our cancellation department at 650-381-2973.
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.