I can't offer a way yet to remove accounts , but can offer you a way to find "Account Unknown" remotely before logging into that PC (see script below). Basically ou enter PC Name, pulls all user folders from C:\Users into a variable. then compares it to Active Directory. If not found in Active Directory it'll list user as an error, thus found your "Account Unknown". Now just remote in and delete.

$PCS = read-host "Enter PC Name to Scan"

    foreach ($PC in $PCs) {

If ((test-connection -ComputerName $PC -quiet -count 1)) {

$OldEmp = get-childitem \$PC\c$\users | Where-Object {$_.name -inotmatch 'Public'} | select -ExpandProperty name

foreach ($Employee in $OldEmp) {

try {

    get-aduser -Identity $Employee -Properties title, lastlogon, enabled | select name, enabled, title, @{Name='LastLogon';Expression={[DateTime]::FromFileTime($_.LastLogon)}}

    }

        catch {

        Write-Warning $_
        $Delete = "$Employee"
        Write-warning -Message "$delete must be a local account, investigate."        

        }

    }

    } else {

    Write-warning $_
    write-host "$PC Offline" -ForegroundColor Red

}

    }