Or more like his creation would now oppose any future invasion and pose an embarrassing threat to the legion. I think he preferred to fight an azeroth as it is now rather than an azeroth full of undead. Not because of the lich kings own power individually but the army he could have had.
Still proves nothing other than the lk who was not frozen to a chair and had a powerful weapon in frostmourne at the time. All it shows is thay we were better than all his forces (yes his elite forces sent to toughen us up) save him alone.and as the previous poster said, The Lich King won at ICC, it was arrogance of having to rub it in Trion's face that lead him to fail.
aka he got cocky and wanted to show off and that showing off is what made him lose.
Does not mean or prove he was more powerful than kiljaeden.
Btw please no more lich king power talk or we may summon a creature who's headcannon is more powerful than you can ever imagine to this thread...