Parent theme CSS overriding child CSS rules

After looking at your parent theme’s source code related to enqueuing styles, the original code you posted looks close. You just need to use the handle from the parent theme, adios-main-style. Add wpse244754_child_theme_enqueue_styles() to your child theme’s functions.php file:

add_action( 'wp_enqueue_scripts', 'wpse244754_child_theme_enqueue_styles' );
function wpse244754_child_theme_enqueue_styles() {

    // Enqueue the parent theme's stylesheet
    wp_enqueue_style( 'adios-main-style', get_template_directory_uri() . '/css/style.css');

    // Enqueue the child theme's stylesheet, specifying the parent theme's
    // styles as a dependency.
    wp_enqueue_style( 'child-style',
            get_stylesheet_directory_uri() . '/style.css',
            array( 'adios-main-style' ) // dependency
    );
}

The child theme’s functions.php (and its includes) will be loaded before the parent theme’s functions.php.

Looking at wpse244754_child_theme_enqueue_styles(), the parent theme’s style.css will be loaded first. We’ve specified adios-main-style as a dependency for the child theme’s styles, ensuring that the child theme’s styles will load after the parent theme’s styles.

When the parent theme tries to enqueue adios-main-style, it won’t be loaded again, thanks to the way that wp_enqueue_style() works.

Another approach
The parent theme’s adios_enqueue_scripts() function is pluggable. So another alternative would be to copy that entire function to your child theme and customize it as needed, e.g.:

function adios_enqueue_scripts() {

    if( ( is_admin() ) ) { return; }

    if ( is_singular() ) { wp_enqueue_script( 'comment-reply' ); }


    // enqueue script
    wp_enqueue_script( 'adios-scrollify',        get_template_directory_uri() .'/js/jquery.scrollify.min.js',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_enqueue_script( 'adios-wow',              get_template_directory_uri() .'/js/wow.min.js',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_enqueue_script( 'adios-count',            get_template_directory_uri() .'/js/jquery.countTo.js',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_enqueue_script( 'adios-isotope',          get_template_directory_uri() .'/js/isotope.pkg.min.js',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_enqueue_script( 'adios-img-loaded',       get_template_directory_uri() .'/js/jquery.imageloaded.js',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_enqueue_script( 'adios-all',              get_template_directory_uri() .'/js/all.js',array('jquery'), ADIOS_THEME_VERSION,true);

    // register script
    wp_register_script( 'adios-gmapsensor', '     http://maps.google.com/maps/api/js?sensor =false',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_register_script( 'adios-swiper',           get_template_directory_uri() .'/js/swiper.min.js',array('jquery'), ADIOS_THEME_VERSION,true);
    wp_register_script( 'adios-cd-google-map',    get_template_directory_uri() .'/js/map.js',array('adios-gmapsensor'), ADIOS_THEME_VERSION,true);
    wp_register_script( 'adios-youtube',          get_template_directory_uri() .'/js/jquery.youtubebackground.js',array('jquery'), ADIOS_THEME_VERSION,true);

    wp_localize_script('adios-cd-google-map', 'get',
        array(
            'ajaxurl' => esc_url(admin_url( 'admin-ajax.php' )),
            'siteurl' => get_template_directory_uri()
        )
    );

    wp_enqueue_style( 'adios-fonts',       adios_fonts_url(), null, ADIOS_THEME_VERSION );
    wp_enqueue_style( 'adios-bootstrap',   get_template_directory_uri(). '/css/bootstrap.min.css',null, ADIOS_THEME_VERSION);
    wp_enqueue_style( 'adios-main-style',  get_template_directory_uri(). '/css/style.css',null, ADIOS_THEME_VERSION);

    // *** Child theme style added here ***
    wp_enqueue_style( 'adios-child-style',  get_stylesheet_directory_uri(). '/style.css', array( 'adios-main-style' ), ADIOS_THEME_VERSION);

    wp_enqueue_style( 'adios-fonttello',   get_template_directory_uri(). '/css/fontello.css',null, ADIOS_THEME_VERSION);
    wp_enqueue_style( 'adios-animate',     get_template_directory_uri(). '/css/animate.css',null, ADIOS_THEME_VERSION);

    // register
    wp_register_style('adios-swiper',      get_template_directory_uri(). '/css/idangerous.swiper.css',null, ADIOS_THEME_VERSION);


    // Custom CSS
    $css_code = adios_get_opt('css_editor');
    $style="";
    $style .= ( !empty($css_code)) ? $css_code:'';
    wp_add_inline_style('main-style', $style);
}
add_action( 'wp_enqueue_scripts', 'adios_enqueue_scripts' );

This approach is overkill if you just want to add a stylesheet for your child theme, but it can be handy if you’re doing extensive customization.