1. Create a new module that will hold your Drupal Console command, such as
   console_commands:

drupal generate:module

// Welcome to the Drupal module generator
Enter the new module name:
 > Console Commands

Enter the module machine name [console_commands]:
 >

Enter the module Path [/modules/custom]:
 >

Enter module description [My Awesome Module]:
 >

Enter package name [Custom]:
 >

Enter Drupal Core version [8.x]:
 >

Do you want to generate a .module file (yes/no) [yes]:
 >

Define module as feature (yes/no) [no]:
 >

Do you want to add a composer.json file to your module (yes/no) [yes]:
 >

Would you like to add module dependencies (yes/no) [no]:
 >

Do you want to generate a unit test class (yes/no) [yes]:
 >

Do you want to generate a themeable template (yes/no) [yes]:
 > 

Do you confirm generation? (yes/no) [yes]:
 >

Generated or updated files
1 - modules/custom/console_commands/console_commands.info.yml
 2 - modules/custom/console_commands/console_commands.module
 3 - modules/custom/console_commands/composer.json
 4  modules/custom/console_commands/tests/src/Functional/LoadTest.php
 5 - modules/custom/console_commands/console_commands.module
 6 - modules/custom/console_commands/templates/console-commands.html.twig

2. Next, we will generate the command's base files using the generate:command command. Call it the disable_users command:

drupal generate:command

// Welcome to the Drupal Command generator
 Enter the extension name [devel]:
 > console_commands

Enter the Command name. [console_commands:default]:
 > console_commands:disable_users

Enter the Command Class. (Must end with the word 'Command'). [DefaultCommand]:
 > DisableUsersCommand

Is the command aware of the drupal site installation when executed?. (yes/no) [no]:
 > yes 

Do you confirm generation? (yes/no) [yes]:
 >

Generated or updated files
 1 - modules/custom/console_commands/src/Command/DisableUsersCommand.php
 2 - modules/custom/console_commands/console.services.yml
 3 - modules/custom/console_commands/console/translations/en/console_commands.disable_users.yml

3. Edit the created DisableUsersCommand.php file and remove the boilerplate example code from the execute method:

/**
 * {@inheritdoc}
 */
protected function execute(InputInterface $input, OutputInterface $output) {
}

4. Update the function to create a DateTime object, representing 10 days ago. We will use this to generate a timestamp for our query:

/**
 * {@inheritdoc}
 */
protected function execute(InputInterface $input, OutputInterface $output) {
  // Get the default timezone and make a DateTime object for 10 days ago.
  $system_date = \Drupal::config('system.date');
  $default_timezone = $system_date->get('timezone.default') ?: date_default_timezone_get();
  $now = new \DateTime('now', new \DateTimeZone($default_timezone));
  $now->modify('-10 days');
}

5. Now, we will add our query, which will query all the user entities who have a login timestamp greater than 10 days:

/**
 * {@inheritdoc}
 */
protected function execute(InputInterface $input, OutputInterface $output) {
  // Get the default timezone and make a DateTime object for 10 days ago.
  $system_date = \Drupal::config('system.date');
  $default_timezone = $system_date->get('timezone.default') ?: date_default_timezone_get();
  $now = new \DateTime('now', new \DateTimeZone($default_timezone));
  $now->modify('-10 days');

  $query = \Drupal::entityQuery('user')->condition('login', $now->getTimestamp(), '>');
  $results = $query->execute();

  if (empty($results)) {
    $output->writeln('<info>No users to disable!</info>');
  }
}

6. Next, we will iterate over the results and mark the user as disabled:

/**
 * {@inheritdoc}
 */
protected function execute(InputInterface $input, OutputInterface $output) {
  // Get the default timezone and make a DateTime object for 10 days ago.
  $system_date = \Drupal::config('system.date');
  $default_timezone = $system_date->get('timezone.default') ?: date_default_timezone_get();
  $now = new \DateTime('now', new \DateTimeZone($default_timezone));
  $now->modify('-10 days');

  $query = \Drupal::entityQuery('user')->condition('login', $now->getTimestamp(), '>');
  $results = $query->execute();

  if (empty($results)) {
    $output->writeln('<info>No users to disable!</info>');
  }

  foreach ($results as $uid) {
    /** @var \Drupal\user\Entity\User $user */
    $user = \Drupal\user\Entity\User::load($uid);
    $user->block();
    $user->save();
  }

  $total = count($results);
  $output->writeln("Disabled $total users");
}

7. Enable the module in order to access the following command:

$ drupal module:install console_commands