Magento 1 Customer Delete Shell Class

customer.php

<?php

require_once 'abstract.php';

class Mage_Shell_Customer extends Mage_Shell_Abstract
{

    /**
     * Run script
     *
     */
    public function run()
    {

        $collection = Mage::getModel('customer/customer')->getCollection()
           ->addAttributeToSelect('firstname')
           ->addAttributeToSelect('lastname')
           ->addAttributeToSelect('email');

        if (!$this->getArg('delete') && !$this->getArg('print')) {
            printf("ERROR: Either --delete or --print must be specified\n");
            exit(1);
        }

        if ($name = $this->getArg('firstname'))
            $collection->addAttributeToFilter('firstname', array('like' => $name));

        if ($name = $this->getArg('lastname'))
            $collection->addAttributeToFilter('lastname', array('like' => $name));

        if ($email = $this->getArg('email'))
            $collection->addAttributeToFilter('email', array('like' => $email));


        foreach ($collection as $item) {
            if ($this->getArg('delete')) {
                printf("Deleting ID:%s\n", $item->getId());
                $item->delete();
            } else {
                printf("%s\t%s\n",
                    str_pad($item->getFirstname() . $item->getLastname(), 50),
                    $item->getEmail()
                );
            }
        }

    }

    /**
     * Retrieve Usage Help Message
     *
     */
    public function usageHelp()
    {
        return <<<USAGE
Usage:  php -f customer.php -- [options]

    --firstname     Filter by first name
    --lastname      Filter by last name
    --email         Filter by email

    --delete        Delete matching users
    --print         Display matching users

USAGE;
    }

}

$customer = new Mage_Shell_Customer();
$customer->run();

Cleaning up created users

Once you've got your mechanisms in place to help prevent further SPAM registrations, its time to clean up the records created. Use this quick shell script for Magento that you can download.

1. Download the gist to the Magento shell directory
   wget --no-check-certificate https://gist.githubusercontent.com/blessani/e700e35d9ecbade2021c8e0f6d95a8c0/raw/28c530b727999a2f7f66e0372eae45bc3ab7c551/customer.php -qO shell/customer.php

2. Execute the script in dry run (print only) using matching data you observed in the Magento admin "Manage customers" pane,
   php shell/customer.php --lastname "%drive.google.com%" --print

3. After reviewing the results, re-run the command with the delete option
   php shell/customer.php --lastname "%drive.google.com%" --delete

src: https://www.sonassi.fr/blog/combating-spam-user-registration-magento#cleaning-up-created-users