And the final boss in the storyline mode is.... ラストサムライ (The Last Samurai)
As the name implies it does have a samurai design to it. Golden color and undead look.
Here's it's full body appearance.
If you were to load it in StudioCCS, a program for viewing models from .hack video games, it looks mangled and twisted until you unravel it manually.
You can get around this by loading this .bin file to load a modified bone structure that I've setup.
LastSamurai.bin