Force Removal of DHCP Server will leave entries in Active Directory. Lets see how to remove it in a proper way.
Open DHCP server. Right Click Unauthorize
As soon as you Unauthorize
Connect to the Configuration Container
Drill down to CN=Configuration | CN=Services | CN=NetServices
you can see DHCP Server entries get removed. You can remove the old ones forcefully from Adsiedit.msc
Now Open Server Manager – remove Roles and Features –
Uncheck DHCP Server. Remove it.
Now DHCP server has been decommissioned successfully.