Kill 25 enemies in Survival Slice to unlock Koi:

Unlock the following equipment by performing the corresponding tasks:

EQUIPMENT - HOW TO UNLOCK
Alternate Armor - Defeat the character you are playing as in Arcade Mode.
Mid Range Weapon - Complete the Slice Challenge in Arcade Mode.
Projectile Weapon - Complete Arcade Mode.
Short Range Weapon - Defeat the Navy SEAL during the first challenge in Arcade Mode.

Unlock the following modes by entering the corresponding cheats at the title menu. Note: Achievements will be locked when any modes are active:

Player 1 God Mode - UP, A, X, B, Y, DOWN.
Player 2 God Mode - DOWN B, X, A, Y, UP.
Slice Mode for Single Player - LT, X, A, X, A, RT.
Sudden Death - X, RB, UP, DOWN, LB, A.
Zombie Mode for Single Player - Y, A(3) X B.

ACHIEVEMENT - HOW TO UNLOCK
Legendary Warrior (10 points) - Win 10 online ranked duels.
These Dice are Loaded! (5 points) - Lose three consecutive battles at even odds or better during a game of Generals.
Six Degrees of Separation (35 points) - Severed every limb from your opponent during a slice mode duel without using a final strike.
Slash Mode (40 points) - Kill 50 enemies in a row in Survival Slice Challenge as the primary player.
Legendary Arsenal (20 points) - Unlock all weapon and armor for each of the Legendary Warriors.
Legendary General (15 points) - Activate all three General Abilities during a single game of Generals.
Marksman (10 points) - Get three consecutive headshots using any long range weapon in a single ranked duel.
When Push Comes to Shove (5 points) - As the primary player, After being pushed knock an opponent out of the ring.
A Pox of the Small Variety (5 points) - Win a ranked online duel against a developer playing as Cortes or someone with this achievement.
Dead and Broken (10 points) - Break your opponent's arm and leg by grappling before final striking them in a ranked duel.
If anyone Khan, Genghis Khan! (35 points) - Beat arcade mode with Genghis Khan using only the dead fish on Deadliest Difficulty.
Denied! (10 points) - Parry your opponent three times in a row without being hit in a single ranked duel.

Unlock the following weapons by performing the corresponding tasks:

WEAPON - HOW TO UNLOCK
Broom - Kill 25 enemies in Survival Slice with Joan of Arc
Farmer's Pitch Fork - Kill 25 enemies in survival slice with Vlad The Impaler.
Fishing Rod - Kill 25 enemies in survival slice with Attila the Hun.
Hand Fan - Kill 25 enemies in survival slice with Sun Tzu.
Koi - Kill 25 enemies in Survival Slice with Genghis Khan.
Shovel - Kill 25 enemies in survival slice with William Wallace.
Toy Scythe - Kill 25 enemies in survival slice with Hernan Cortes.
Tribal Flute - Kill 25 enemies in survival slice with Shaka Zulu.
Umbrella - Kill 25 enemies in survival slice with Alexander the Great.
Wooden Spoon - Kill 25 enemies in survival slice with Hannibal.

Unlock the following awards by performing the corresponding tasks:

AVATAR AWARD - HOW TO UNLOCK
Sun Tzu's costume - Complete Arcade mode with any warrior.
Sun Tzu's helmet - Complete Arcade mode as each warrior under the Deadliest difficulty setting.