If your site's been configured to sync new accounts from your accounting software to the website, you try to remove it by disabling the account as a "web enabled" account in your accounting package, and then running Webninja's sync - but the account remains online after this.
The syncing of accounts from your accounting package to the website only works one way, from the accounting software to the website. The sync doesn't remove existing online user profiles if the corresponding account in your accounting system is disabled from showing online.
You'll need to :
a) disable the account as a web account in your accounting system
b) delete the online account from the Webninja CMS Admin in the "View Customer List" section: