How about a "Won the battles, but lost the war" achievement for winning all your games in a tournament, but still not winning overall? This would apply to triple gammon tournaments only.
As an example, this happened to Erinity and me in different sections of Madhouse 2008 - Week 4
Possibly have a minimum number of players in a section to get the achievement, or have a separate, higher-scoring achievement for doing it with 7 or 8 players in your section?
(Cacher) Vous pouvez envoyer un message à vos amis avec juste un clic en les ajoutant à votre liste d'amis puis en cliquant sur la petite enveloppe à côté de leur pseudo. (pauloaguia) (Montrer toutes les astuces)