This achievement is story related and cant be missed.
Its straight forward boss fight with El Trio de la Muerte. It comes in 3 parts.
PART 1
First part is breaking his shield with a combo, then attacking in your usual fashion while avoids the musical notes.
PART 2
Picking up the bad guys with 'Y' and throwing them at the boss. Then attack as usual when he is dazed.
PART 3
This is where you will probably die a few times. But no threat you can keep retrying! You must attack all three heads when they are not dimmed (This will make sense when you play) all while avoiding the music blasts. You will know when to move as before a blast notes start to appear on the side it will be fired from.
Once all three heads are disabled you will get the achievement :)
Below is a video for anyone not interested in the block of text above.