When you are removing a child domain with NTDSUTIL you will receive the following error:

DsRemoveDsDomainW error 0x2015 (The directory service can perform the requested operation only on a leaf object.)

If this happen, follow below mentioned steps. When you are done you can follow this article to remove child domain.

Open PowerShell with elevated privileges and execute the following commands in sequence.

When domain controllers are taken offline without being demoted first, the domain metadata is still left in Active Directory. This article illustrates how to remove that domain metadata with the help of NTDSUTIL utility.

Open PowerShell with elevated privileges and execute the following commands in sequence.

Step 1. Type ntdsutil and hit enter from keyboard

When you promote the server to domain controller and failed, you are still left with its metadata inside Active Directory Domain. Because of this, you may face some of the following issues: 

There are two ways you can use to start service with a specific user account; GUI and PowerShell (I call it shiny method). However, we will look into both methods.

Starting a Service with Specific User Account Using GUI

Type services.msc in Run and then click Enter from the keyboard. Find the desired service. Right-click it and then click Properties