add_action('init', function() {
    if (!isset($_GET['delete_posts'])) return;

    global $wpdb;

    $batch = 5000;

    $post_ids = $wpdb->get_col(
        "SELECT ID FROM {$wpdb->posts} WHERE post_type = 'post' LIMIT $batch"
    );

    if (empty($post_ids)) {
        echo "Done.";
        exit;
    }

    $ids_str = implode(',', array_map('intval', $post_ids));

    $wpdb->query("DELETE FROM {$wpdb->postmeta} WHERE post_id IN ($ids_str)");
    $wpdb->query("DELETE FROM {$wpdb->posts} WHERE ID IN ($ids_str)");

    echo count($post_ids) . " posts deleted.";
    exit;
});
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /home/standa9/public_html/wp-content/mu-plugins/index.php:1) in <b>/home/standa9/public_html/wp-includes/feed-rss2-comments.php</b> on line <b>8</b><br />
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	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:atom="http://www.w3.org/2005/Atom"
	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
	
	>
<channel>
	<title>
	Comments on: Star Challenge Mission 1: &#8216;Dark Dodger&#8217;	</title>
	<atom:link href="https://solar2.standardof.net/solar-2-guide/star-solar-system-stage/dark-dodger/feed/" rel="self" type="application/rss+xml" />
	<link>https://solar2.standardof.net</link>
	<description>Helping You Get Better at Games to Impress Your Mother</description>
	<lastBuildDate>Wed, 14 Oct 2020 12:54:40 +0000</lastBuildDate>
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	hourly	</sy:updatePeriod>
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	1	</sy:updateFrequency>
	<generator>https://wordpress.org/?v=6.5.10</generator>
</channel>
</rss>