How to create a widget like this?

Question

Your question is a little short on detail, but let’s suppose you have retrieved the posts using wp_query and are looping through it like this:

$the_query = new WP_Query( $args );
if ( $the_query->have_posts() ) {
    while ( $the_query->have_posts() ) {
        $the_query->the_post();
        STUFF
        }
    wp_reset_postdata();
    }

In the position of STUFF you want to distinguish between the first post and other posts in which elements you want to retrieve. You can do this by accessing $current_post, which holds the number of the post inside the loop. You would get this:

if ($the_query->current_post == 0) {
  // retrieve featured image, title and content }
else {
  // retrieve title only }