To delete multiple clients and their reports, go to Client & Report Library from the Libraries dashboard, select the clients you wish to delete and click the 'Delete X selected clients' button.

You will only be able to delete the clients and reports belonging to another user within your account if view all user's clients / reports has been activated for your account, and as a result, the 'Owned by' field shows in your Client Library.

Deleting multiple clients with multiple reports may take a little time - please be patient.