Query all posts and not repeat the same tag

You can try something like this:

<?php

$tags_array   = get_tags();
$news_query  = new WP_Query;

foreach ( $tags_array as $tags ) :
    $news_query->query( array(
        'cat'                 => $tags->term_id,
        'posts_per_page'      => 1,
        'no_found_rows'       => true,
        'ignore_sticky_posts' => true,
    ));

    ?>

    <h2><?php echo esc_html( $tags->name ) ?></h2>

    <?php while ( $news_query->have_posts() ) : $news_query->the_post() ?>

            <div class="post">
                <?php the_title() ?>
                <!-- do whatever you else you want that you can do in a normal loop -->
            </div>  

    <?php endwhile ?>

<?php endforeach ?>