How to Demote and Remove Domain Controller and ADDS role from server 2008 r2
Removing the AD DS roles with Dism.exe or the Windows PowerShell DISM module after promotion to a Domain Controller is not supported and will prevent the server from booting normally.
Unlike Server Manager or the ADDSDeployment module for Windows PowerShell, DISM is a native servicing system that has no inherent knowledge of AD DS or its configuration. Do not use Dism.exe or the Windows PowerShell DISM module to uninstall the AD DS role unless the server is no longer a domain controller.
The -credential argument is only required if you are not already logged on as a member of the Enterprise Admins group (demoting last DC in a domain) or the Domain Admins group (demoting a replica DC).The -includemanagementtools argument is only required if you want to remove all of the AD DS management utilities.
Warning
Do not select this option unless the domain controller cannot contact other domain controllers and there is no reasonable way to resolve that network issue. Forced demotion leaves orphaned metadata in Active Directory on the remaining domain controllers in the forest. In addition, all un-replicated changes on that domain controller, such as passwords or new user accounts, are lost forever. Orphaned metadata is the root cause in a significant percentage of Microsoft Customer Support cases for AD DS, Exchange, SQL, and other software.
If you forcibly demote a domain controller, you must manually perform metadata cleanup immediately. For steps, review