function remove_all_image_sizes() {
    foreach ( get_intermediate_image_sizes() as $size ) {
            remove_image_size( $size );
    }
}
 
add_action('init', 'remove_all_image_sizes');

add_filter( 'intermediate_image_sizes_advanced', 'prefix_remove_default_images' );
// This will remove the default image sizes and the medium_large size. 
function prefix_remove_default_images( $sizes ) {
 unset( $sizes['small']); // 150px
 unset( $sizes['medium']); // 300px
 unset( $sizes['large']); // 1024px
 unset( $sizes['medium_large']); // 768px
 return $sizes;
}