Remove image sizes

add_filter( 'intermediate_image_sizes_advanced', 'hoge_remove_default_images' );
function hoge_remove_default_images( $sizes ) {
    unset( $sizes['small']); // 150px
    unset( $sizes['medium']); // 300px
    unset( $sizes['large']); // 1024px
    unset( $sizes['medium_large']); // 768px
    return $sizes;
}