How to remove your Nintendo Club account

Use the webform located here to request account removal. https://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.

Direct removal link: https://www.nintendo.com/consumer/webform.jsp

Helpful Trick: Removing online data

Publicly visible text/images often aren’t properly removed even when you succeed in removing an account. Try editing or removing them manually before removing the account itself. If you’re unsure what happens to your tracks: this can be found mostly in the Terms of Service/Privacy Policy; otherwise you can always contact Nintendo Club and ask personally. By the way, removal requests don’t necessarily mean your data will actually be removed (e.g. due to legal obligations).

Helpful Trick: Remove third-party logins

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 here to find out how.