This post summarizes and lists down the information you need to solve the specific error which occurs when you try to delete a AAD.

There are plenty of articles for this and I recommend to read the link below which explains very frequent error messages of AAD and the fixes.

https://support.microsoft.com/en-us/kb/2967860

Also read this blog for a detailed description.

http://alexmang.com/2015/06/directory-contains-one-or-more-applications-that-were-added-by-a-user-or-administrator-solution/

Some useful information

In order to manage the AAD using PowerShell we need to install two components.

1. AAD Module for PowerShell
2. Microsoft Online Services Sign-in Assistant

See the below article on how you can accomplish this.

https://onlinehelp.coveo.com/en/ces/7.0/administrator/installing_the_windows_azure_ad_module_for_windows_powershell.htm

Quick Steps

1. Login to Azure Portal using your service administrator account.
2. Make sure there are no users or other external applications. (If you find any of them delete them)
3. Create a Global Admin user in the AAD you want to delete.
4. In the PowerShell, login as the created Global Admin user
5. Run the following script
6. You will get error messages as mentioned in Alexe’s Blog but you can simply ignore them.
7. Then go to the portal and delete the created Global Admin user.
8. And finally delete the AAD.