Today we're going to scorch a device from MEM and Azure AD. Let's get started.

Removing a Device from Users and Computers (Active Directory on Prem)

These steps will only apply to Hybrid AD Devices. If your device is not Hybrid AD then move onto the next step.
Open Users and Computers (Active Directory)
Right click on “co.ssd.k12.mo.us” and select Find…
Type in the Computer name of the object you’re looking for
Right click on that object and delete it

Removing a Device from Endpoint Manager and Autopilot

You will need to have access to Azure AD and Microsoft Endpoint Manager on a device that's not being scorched.

We are going to be working in Endpoint Manager. You can use Chrome or Edge for good results.

Record the serial number of the device that needs to be removed.
1. In my example you'll find that I'm working on device 5X38M63.
Log into Office 365.
Either using the tiles to the left of your screen or selecting the "Waffle" in the top left look for the Admin tile.
Select the Admin Tile.
The tile looks like this and will open a new screen:
Select "Show All" on the left menu area.
Select "Endpoint Manager".
Chose "Devices" on the left panel.
Chose "Windows".
You can search for the device by its Serial Number.
Select the record you want to work with.
Caution - The Device Name will be the same as the Azure AD Device record. If its different than SSD-Serial# then make a note of it.
Select the Delete option (Looks like a trash can).
Select "Yes" when asked to confirm deleting the record.
Next we'll need to remove the Autopilot record from MEM.
Click Devices.
Click Enroll Devices.
Under "Windows Autopilot Deployment Program" select Devices.
Put the serial number of the device you want to check up on here.
Check the box to the left of the box of the device we want to remove.
Click the "Delete" option.
Select the "Yes" option to confirm the operation.
If you click the bell icon you can see the status of the deletions taking place. Autopilot deletion will take several minutes. You don't have to wait. You can move onto the next step.

We are going to work in Azure Active Directory. Chrome or Edge both work to do this.

You may skip the first few steps if you know how to navigate to Azure Active Directory.

Log into Office 365.
Either using the tiles to the left of your screen or selecting the "Waffle" in the top left look for the Admin tile.
Select the Admin Tile.
The tile looks like this and will open a new screen:
Select "Show All" on the left menu area.
Select "Azure Active Directory".
You will select "Azure Active Directory" again on the panel on the left.
Select "Devices".
Search for the device name. In my case I'm looking up SSD-5X38M63. In most cases (While we're in a Hybrid environment) there will be two results.
Select all matching device records.
When you do this the trash can icon with the selection "Delete" will be available. Chose this.
If the records do not delete then its likely there's something connected to MEM still.