I believe that's default with Operating System and can not be deleted , Removing DefaultAccount and guest account is not possible, however you can disable these accounts if there available on the logon screen.
You can use the following command to disable them. For disabling DefaultAccount : Net user DefaultAccount/active:no
For disabling the guest account: Net user guest /active:no
Hope this answers your question :)
--If the reply is helpful, please Upvote and Accept as answer--