To view all accounts that are older then 3 days and have never logged in:
SELECT * FROM `realmd`.`account` WHERE DATE_SUB( CURDATE( ) , INTERVAL 2 DAY ) >= `joindate` AND `last_login` = '0000-00-00 00:00:00';

To remove the above accounts:
DELETE FROM `realmd`.`account` WHERE DATE_SUB( CURDATE( ) , INTERVAL 2 DAY ) >= `joindate` AND `last_login` = '0000-00-00 00:00:00';