Here is the full list of all 28 Warbands: Bushido achievements.
Win 100 battles with only one unit left
Win 50 battles with only one unit left
Complete Samurai scenario on Insane difficulty
Complete the main campaign
Complete Cutthroats scenario on Insane difficulty
Win 10 battles with only one unit left
Get 5000 coins
Kill 8 enemies with one unit in a single combat
Kill a 4WP unit or higher with peasant
Kill 200 enemies with ranged units
Use Hand of Destiny card 100 times
Make 3000 points of damage
Kill 5 enemies with one unit in a single combat
Use Hand of Destiny card 50 times
Get 1000 coins
Win 15 battles without losing a single unit
Get 500 coins
Kill 200 enemies with melee units
Make 1000 points of damage
Kill 50 enemies with ranged units
Win 5 battles without losing a single unit
Make 500 points of damage
Kill 3 enemies with one unit in a single combat
Kill 50 enemies with melee units
Kill 10 enemies with ranged units
Use Hand of Destiny card 10 times
Win battle without losing a single unit
Kill 10 enemies with melee units