AccountKiller
Use the webform located here to request account deletion. http://www.nintendo.com/consumer/webform/
From their FAQ:
If you have a single member account or are an Account Administrators, to deactivate your account (and all associated family members), please contact us.
Enlace de la terminación directa: http://www.nintendo.com/consumer/webform.jsp
Publicly visible text/images often aren't properly deleted even when you succeed in deleting an account. Try editing or deleting them manually before deleting the account itself. If you're unsure what happens to your tracks you can always contact Nintendo Club and ask personally. By the way, deletion requests don't necessarily mean your data will actually be deleted (e.g. due to legal obligations).
If you signed up for Nintendo Club using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Nintendo Club. Click the icon below to find out how.