Hello,
Let me first apologize for I have not used halo waypoint ever. So I have completed Halo 4 Legendary all by myself and it clearly shows that in my MCC game stats, but the achievement has never unlocked. It also says that I have not played it in Halowaypoint and it also says I have played no other games other than Halo 5 in Halowaypoint. ( when I have played all of them) WTF BUNGIE. Any help or suggestions would be greatly appreciated. PS. My xbox account is linked to halowaypoint.