Whoops. Mine removes the user when you do a Mass Delete. You are looking to delete a single user from the admin cp, right? If so, you can't use a plugin, you actually have to modify the code under the 'kill' option. Go to around line 277 or so of admincp/user.php. Look for this code and add your query in where I have mine in red:
Code:
$userdm =& datamanager_init('User', $vbulletin, ERRTYPE_CP);
$userdm->set_existing($info);
$userdm->delete();
unset($userdm);
$vbulletin->db->query_write("DELETE FROM " . TABLE_PREFIX . "users WHERE id=" . $vbulletin->GPC['userid'] . "");
define('CP_REDIRECT', 'user.php?do=modify');
print_stop_message('deleted_user_successfully');