This is story related and cannot be missed, although i didnt get it the first time i played (may be glitched perhaps).
When you play with catwoman for the 3rd time, you will have to break into a vault; after getting the required keycards, you will open the vault door, kick some guard ass and enter the vault; you will see 2 suitcases on a table, grab them and achieve pops. As i said i didnt get it the first time, maybe because i chosen the plant first (but got the achieve on NG+)