Code snippet that can use to delete users by role in drupal 8.
<?php
/**
* hook_cron()
*/
function mymodule_cron()
{
$role = 'editor';
$ids = \Drupal::entityQuery('user')
->condition('roles', $role)
->execute();
$users = \Drupal\user\Entity\User::loadMultiple($ids);
foreach ($users as $user) {
$user->delete();
}
}
