How to delete a 2nd Administrator account?

Surface Pro 7+ laptop with 1 admin and 1 user account.
Worked well, until I messed up things in an attempt solve a software issue.
Deep sigh....

From within the 2nd account, I created a 2nd "Local Administrator".
Did not think it over properly, some software required admin rights to be updated

So, right now, I have:
'Me' as administrator
My wife as user
and a local administrator.
Note that the setup of this 'local admin' has not been completed.

I would like to get rid of the last one.

Any suggestions?

Thanks in advance.
(Windows 10 x64)

Regretfully under 'Other Users' there is nothing ("3" in the above tutorial)
Check C:\Users

There is a folder \Administrator, with a lllot of subfolders.
Don't know, maybe I should simply delete that folder.

Yes, I can log into that account.
For info - run Netplwiz tried to change the role and name (UserX) and remove, but no go.
From netplwiz ->Advanced tab to lusrmgr, see attachment.

As said, I could not install an update on 'Guests' (of course not) but then took the wrong decision/didn't think it over and followed some tutorial that sets up administrator from the command prompt. Stupid, stupid, I know...

It seems though that nothing can be done to correct that.

Well, except maybe a Windows reset then.
Built-in account and I seem to be unable to make changes to that, so it is there to stay.

What I ultimately could do is that to check the "Account is disabled" option (Lusmgr > UserX > Properties > General)
at least it doesn't show up on the Windows startup screen... phew.. what a drama.

dalchina said:

Please see post #4 your repeat arrived as I was typing.

Oops, sorry..