Here is the full list of all 12 Black & White Bushido achievements.
Get 10 kills while in the water
Play a 4 player Local Game 1 time
Clash in Mid Air 10 times
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
Kill an enemy after teleporting above them (10 times)
Slice up the Shark 1 time
Get 300 or over in CHALLENGE MODE
Get 3000 or over in CHALLENGE MODE