This is a simple example where we unpublish a users posts if their account goes minus 20 points.

Unpublish posts for negative balances

/**
 * Unpublish users Posts
 * If a user reaches or exceeds the minimum balance
 * we unpublish all their posts.
 * @version 1.0
 */
add_filter( 'mycred_add', 'mycred_unpublish_posts_on_minus', 999, 3 );
function mycred_unpublish_posts_on_minus( $reply, $request, $mycred ) {
	if ( $reply === false ) return;
	
	// Get users current balance
	$current_balance = $mycred->get_users_cred( $request['user_id'], $request['type'] );
	
	// Max negative balance
	$max = -20;
	
	// Check balance
	if ( $current_balance <= $max ) {
	
		// User has reached the max, unpublish all their posts
		global $wpdb;

		// Change ALL posts to pending for this user.
		$wpdb->query( $wpdb->prepare( "
			UPDATE {$wpdb->posts} 
			SET post_status = %s 
			WHERE post_author = %d 
				AND post_status = %s;". 'pending', $request['user_id'], 'publish' ) );
	
	}

	// Always return a reply
	return $reply;
}