Full list of all 12 Carcassonne achievements worth 200 gamerscore. It takes around 8-10 hours to unlock all of the achievements on Xbox 360.
Score a City with 3+ tiles in Single Player
Score a road with 5+ tiles in Single Player
Score a Farm supplying 4+ Cities in Single Player
Score 50+ points in Single Player
Win 1 Ranked game
Score a total of 2000+ points from all your Carcassonne games combined
Win a Player Match against 3 or more opponents
Score 150+ points in a Single Player game
Score a City with 9+ tiles in a Player Match vs. 2 or more opponents
Score 2 adjacent Monasteries in Single Player
Beat an opponent in a Player Match by 50+ points
Score a total of 5000+ points from all your Carcassonne games combined