Originally Posted by RichjB
I have done that many times so far and have not unlocked that Achievement. Right now I only have a few more items left before I max all of them out.
Maybe you have to pick up all the items within the game to unlock this. If I'm wrong on this, someone please feel free to correct me.
You need to max out all of the Vital Stars (S,M, and L), both Devil Stars (S and L), max holy waters, max gold orbs, max purple orbs, and max blue orbs (from the shop, the levels, and the secret missions). You don't need to pick up all of the items in the levels (except blue crystals which you do need to max blue crystals).