To unlock the "Card Collector" achievement on Steam, you need to win all the Gwent cards. I provide a save where Geralt stands near the blacksmith, you need to win the last card from him. After winning, the achievement will be yours. No DLC was used in the save, so it will work on all versions.

The plot is completely completed, level 35, master armor of the cat school

The files from the archive should be placed in the path C:Users(Username)DocumentsThe Witcher 3gamesaves