I think one of the more extreme ones is DOH-TYO 9 hours whereas TYO-DOH is 12 hours! It surprised me the first time I flew this route!
Also, on MMB after a minor flight time change my TXL-DOH flight is listed as 4 hours 50 minutes. I went onto MyFlights which lists the flight as 5 hours 50 minutes.... I assume this is another error?