Way of the Samurai 3

You'll get this after having gone through 99% of the possible endings in the game. It can be difficult to figure out what you have to do to get each and every ending. There are 22 of them but only 21 of them are required for this achievement. There are many different paths to get to each ending as well so even with a guide it can be touch and go at times. So I'm going to include two links to help you track down the endings your looking for.

SephirothsAwakening's Channel Has videos he made that cover the play through for each ending.
http://www.youtube.com/user/SephirothsAwakening

Joel Fox has a text guide up on IGN that can be helpful for the entire game as well as the endings.
http://faqs.ign.com/articles/105/1054666p1.html

Both of these are based off the PS3 version so you'll have to make mental notes about the button differences, but other than that the information is all the same.