10man and 25man ICC Lich King achievement are giving the same title currently in WoW Classic. They are supposed to be different. 10man is supposed to give “Bane of the Fallen King” , 25man gives “the Kingslayer”.
Both 10 and 25m normal give kingslayer.
10m heroic is bane of the fallen king and 25m heroic is light of dawn.
You cant see the heroic achieves till you get the normal ones.
Oh, my mistake!