Here is the full list of all 12 Black & White Bushido achievements.
Slice up the Shark 1 time
Kill an enemy from Stealth Movement while in your own color
Get a double kill 10 times
Kill an enemy with a Shuriken from Screen wrapping
Win a game of capture the flag without losing a flag
Kill an enemy just before they capture the flag 10 times
Play a 4 player Local Game 1 time
Kill an enemy after teleporting above them (10 times)
Clash in Mid Air 10 times
Get 10 kills while in the water
Get 300 or over in CHALLENGE MODE
Get 3000 or over in CHALLENGE MODE