I do need to point out this achievement is glitched. Here's what I recommend doing just in case it happens to you. Make sure you have save states in every game about to defeat the final boss. You have to beat them all in any order to get this achievement. Personally I started with Castlevania to Kid Dracula after my Castlevania run. Just like most achievements, wait a little bit during the endings before going to the next game. This method makes getting the biggest achievement a lot easier.