Foren / Cotonti / Support / How to mass delete Banned members ?

I would say: go to phpmyadmin and execute a single sql query... There's no such way unless it's a self-made plugin.

I see what you mean :)

Then the plugin would be okay. There was the usermanager plugin somewhere available, it had a couple of bugs but it would be a good base to start.

Here is the code from system/core/users/users.edit.inc.php:

$sql = sed_sql_query("SELECT * FROM $db_users WHERE user_id='$id'");

			if ($row = sed_sql_fetchassoc($sql))
			{
				if ($cfg['trash_user'])
				{ sed_trash_put('user', $L['User']." #".$id." ".$row['user_name'], $id, $row); }
				$sql = sed_sql_query("DELETE FROM $db_users WHERE user_id='$id'");
				$sql = sed_sql_query("DELETE FROM $db_groups_users WHERE gru_userid='$id'");
				if ($ruserdelpfs) { sed_pfs_deleteall($id); }
				sed_log("Deleted user #".$id,'adm');
				header("Location: " . SED_ABSOLUTE_URL . sed_url('message', "msg=109&rc=200&id=".$id, '', true));
				exit;
			}

What you need to change in your plugin is the main select query. Something like this:

SELECT * FROM $db_users AS u LEFT JOIN $db_users_groups AS g ON g.gru_userid = u.user_id WHERE g.gru_groupid = 3

And of course changed if to while and remove sed_log/header/exit lines from the loop.