How to change label pass field on registration form
Here is the soluition (need to clear the caches):

function MYMODULE_element_info_alter(&amp;$type)
{
    // dpm($type);
    // assuming it's a password_confirm type
    $type['password_confirm']['#process'][] = 'custom_pass';
}

function custom_pass($element)
{
    $element['pass1']['#title'] = 'Пароль / Password';
    ...

    return $element;
}