I had KK pre in a 6 max 25NL zone poker other day , i raised, villain insta shoved full stack (I had about 60 , he had about 25), he shows AKo, hits an Ace on the flop. Now in most cases, esp deep I'm calling all day everyday with KK pre because I want to be against hands like AK and lower pairs.
But I don't think shoving all in full stack with AKo in a cash game against someone whose raising you is good poker. If tables were turned I'd call the raise and if I hit the Ace, id bet or re-raise if the board is good for it.
AK is definitely a weaker hand , it's behind far more often than it's ahead pre flop. 22 can beat AK. Remember that.