If you would like your account to be deleted, send an e-mail to email@example.com with your username, the e-mail address associated with your account, and the statement “please delete my account.” Once deleted, your account/post count cannot be retrieved. You should receive an e-mail once your account has been deleted; this normally takes a few days.
Make sure you're positive you want your account deleted before you send the e-mail- if you send another e-mail afterward, changing your mind, it may not be read before your original e-mail and may not be seen before the account is deleted. Once an account is deleted, all of the information associated with the account is permanently deleted and cannot be retrieved or recovered. So only send an e-mail if your absolute final decision is to have your account deleted.
Accounts are not deleted for anyone with one or more warnings (or a ban) associated with their account, or for users who do not follow the above instructions completely. They are also not deleted an unlimited amount of times- if you ask to have your account deleted more than once a month, it may result in a warning (which means it will not be deleted again), so please make your decision wisely.