For those wondering, all you have to do to earn this achievement is beat the game with each of the four characters in version B. You do NOT have to make it to the 2nd loop and defeat the true boss. In fact, I'd recommend continuing before you get to the final boss because the 2nd loop will make the path to this achievement even longer. I watched the entire ending and credits for each character. The achievement should pop right at the beginning of your final character's ending movie.