Adding function from parent theme to child theme

In your child functions file, try:

remove_action('admin_init', 'kioken_builder_init');

function ben_kioken_builder_init() {

    if ( defined('WPB_VC_VERSION') ) {         
       //etc
    }    
}
add_action('admin_init', 'ben_kioken_builder_init');

You don’t need the if(is_admin()) check because admin_init only fires on admin pages.