Serious sAm BFE Are You Serious Save Pal

Having tested the save it did not unlock the achievement. It just gave me the achievement for beating a level in single player. I reckon that the mission you have beat o serious are tied to you gamertag and not the save file overall.

Please delete this tread as it is useless.

I think you need to complete all the missions on the same difficulty to unlock the achievement.

I see what you mean now.