Use the Level 60 Save First.
As this achievement legitimately would pop before the shopaholic achievement. This is because you have the be 3rd prestige to buy one of the characters.
This is a level 59 character that only needs 1000xp to get to level 60. Just play one game and then once the game has finished the achievement will pop.
The Shopaholic save is a Level 60, 3rd Prestige save (the highest you can get).
- You need to go to Character Selection
- Then go to Survivors 1
- Then click on the Secondary gun which is the Sawn Off Shotgun
- Then buy the Rapid Fire Upgrade and the achievement will pop.
I just hex modded these saves for these achievements for myself and thought id share them on here.