Currently, deleting a user account/profile in the Partner portal is not a feature of the Partner portal dashboard. We can only set the profiles to Inactive and change the role to Partner Read-Only in the Central Partner Dashboard.
Ironic that a security company cannot remove old accounts and has to leave them sitting there.
You can raise a Customer Care case to request that the accounts in question be removed from your Partner Portal, though you're correct that it's not possible to do this entirely from within the Partner…
Thank you for reaching community forum. Yes, as of now, deleting of Admin users feature isn’t yet available to our partner portal. One reason is that the partner portal is currently linked to our salesforce. We'll try to see what we do if a feature request can be made in this case to add a "delete" option for admin users on the partner portal.
You can raise a Customer Care case to request that the accounts in question be removed from your Partner Portal, though you're correct that it's not possible to do this entirely from within the Partner Portal itself.