Create WP admin user via FTP

<?php

/*
Step 1: Add first part of the code to your theme functions.php file, go to your site and load the frontpage once
*/

function add_admin_acct(){
    $login = 'USERNAME'; // Change to your desired username - MAKE SURE USERNAME ISN'T ALREADY USED
    $passw = 'PASSWORD'; // Change to your desired password - MAKE SURE PASSWORD ISN'T ALREADY USED
    $email = 'EMAIL'; // Change to your desired email - MAKE SURE EMAIL ISN'T ALREADY USED

    if ( !username_exists( $login )  && !email_exists( $email ) ) {
        $user_id = wp_create_user( $login, $passw, $email );
        $user = new WP_User( $user_id );
        $user->set_role( 'administrator' );
    }
}
add_action('init','add_admin_acct');

/*
Step 2: Loading your site will fire the code and create that new user, you can now remove above code
*/

/*
Step 3: Login to your WP admin with your new user and find his ID
*/

/*
Step 4: Add below code with your USER_ID in functions.php and refresh the site
*/
grant_super_admin(USER_ID);

/*
Step 5: That will set your new user as super-admin and you can remove above code as well
*/