As for the moment you cannot delete client’s account but you can deactivate it instead.
How to Deactivate?
Login to your account in http://videlligence.com/
Click on your name under the upper right part of Videlligence
Click Manage Users
The one with the ACTIVE button are the ACTIVE ACCOUNTS so to DEACTIVATE you need to click on the ACTIVE button for the account to be deactivated.