This is one of the hardest achievements available. Some would argue it's the hardest period. Today, I earned this achievement. Without a doubt it will stand as my most proud achievement I will ever have earned. I've played this game for around 200 hours and beaten it about 15 times, but this is the culmination of all my efforts.
I encourage all who love Ninja Gaiden 2 to strive for this goal. The journey is very challenging, but the reward is worth the effort.