While attempting to remove the local administrator account from vCenter Server, the following issues were reported:
Unable to remove the Administrators group from the default Administrator role at the vCenter Server top-level permissions tab.
The removal operation fails, generating the following error message:
The requested change cannot be completed because it could leave the system without full administrative privileges for a user or group.VMware vCenter Server
To resolve this issue, assign the Administrator role to an alternate user or group before removing the local Administrators group from the vCenter Server Administrator role.
Steps to Assign the Administrator Role:
Navigate to the Permissions tab in vCenter Server UI.
Right-click within the pane and select Add Permission.
Click Add, then select the desired user or group.
From the Assigned Role drop-down menu, select Administrator.
Verify that the Propagate to Child Objects checkbox is selected, and then click OK.