Here is the full list of all 15 The Iron Union achievements.
Easy Model Stage1 Get All Star
Easy Model Stage2 Get All Star
Easy Model Stage3 Get All Star
Easy Model Stage4 Get All Star
Easy Model Stage5 Get All Star
Hard Model Stage1 Get All Star
Hard Model Stage2 Get All Star
Hard Model Stage3 Get All Star
Hard Model Stage4 Get All Star
Hard Model Stage5 Get All Star
Hell Model Stage1 Get All Star
Hell Model Stage2 Get All Star
Hell Model Stage3 Get All Star
Hell Model Stage4 Get All Star
Hell Model Stage5 Get All Star