function delete_all_comments() {
      $pending_comments = get_comments( array(
        'status' => 'hold',
        'number' => 1000, // Increase this number if you have more than 1000 pending comments
    ) );
    $spam_comments = get_comments( array(
        'status' => 'spam',
        'number' => 1000, // Increase this number if you have more than 1000 spam comments
    ) );
 
    foreach ( $pending_comments as $comment ) {
        wp_delete_comment( $comment->comment_ID, true );
    }
 
    foreach ( $spam_comments as $comment ) {
        wp_delete_comment( $comment->comment_ID, true );
    }
}
 
add_action( 'init', 'delete_all_comments' );