Can't delete a user from users and groups on Catalina

Hey all, I am having some issues I was hoping you all could help with. I purchased a late 2012 Mac mini running Catalina from a shop that refurbishes them. It came with an account called "user" as admin with no password. I created a new account for myself and cannot seem to delete the "user" account.

I go to users and groups, unlock the pad lock, select the "user" and hit the (-). it comes up with a prompt to type in the users password and I hit enter as there is no password on that account. the pop up goes away but the account remains.

I have also followed the steps to go into the Director Utility and delete it that way but it also did not work. I found the user, hit the minus, and it remains.

I also tried to create a password for the account and it won't let me.

Any ideas? Any assistance is greatly appreciated.

Thank you all.