Personally 2001. I still remember that day against Carlton at Optus Oval when they were totally thrashed. Believe it or not, that defeat was the turning point for the Lions. They decided as a team that they weren't going to embarass themselves or their supporters (especially Melbourne based ones) like that again. The next week they lost a close one to Adelaide after a much better performance and then they never lost another game all season. I think they won the last 16 or 17 games of the season and became totally unstoppable. Despite a few Essendon players playing injured in the final, that was still a great Bombers team they beat that year.