Delete account on Mac OS Catalina Single User Mode

In this case, I would recommend the following solution if you don't have FileVault enable :

1. Restart your Mac while holding down Command+ R. Release the keys when the Apple logo and a progress bar appear. This will boot Recovery Mode.

2. When the macOS Utilities window appears, select Disk Utility and continue.

3. Select your startup disk in the pane to the left and take note of its name. (It is usually named Macintosh HD). If the name is greyed out, or if you see the text "Not Mounted", click the Mount button. If requested, select your username and enter your password. Make sure that the startup disk is mounted before continuing.

4. Quit Disk Utility. The macOS utility window should appear.

5. Go to the top menu bar (where the Apple logo resides) and click on Utilities. Select Terminal from the drop-down menu.

6. Enter the following command, exactly as shown. Substitute "startup disk" with the actual name of your startup disk.

   rm '/Volumes/Macintosh HD/var/db/.AppleSetupDone'
   

7. The command line should return with no response. Restart your Mac and it will launch Setup Assistant. If your Mac has FileVault enabled, you'll need to log in after the restart.

You'll be prompted to create a new administrator account. Give it a separate name to easily distinguish it from your real account. When done, complete the rest of the Assistant. I have done this in Catalina and tested. It works perfectly.

Catalina 15.4 /sbin/mount -uw /System/Volumes/Data rm var/db/.AppleSetupDone Exit

Note: This admin is not added to “fdesetup” list , Recovery Console or SingleUser Mode. You will need to create one from the GUI.