Here is the full list of all 25 Legend of Kay Anniversary achievements.
Win the fight against Minister Shun, Lord of the Gorillas
Collect all the three different armour types
Win the fight against Alchemist Tak, King of the Rats
Win the fight against The Dreaded Chei Ni
Win the fight against Qian Bei the Ancestor
Win the fight against Shun's Bodyguard
Win the fight against Jia-Gu
Upgrade your extra-lives to 9
Collect all Swords in the game
Get a 20 X Combo
Get a 15 X Combo
Get a 10 X Combo
Finish the first boar race
Complete the second fight training lesson
Get a 5 X Combo
Win the first fight against the boar
Complete the first sword training
Finish the game on „Hard“ difficulty
Upgrade your Health Points to the maximum
Upgrade your Chi Points to the maximum
Collect all Claws in the game
Collect all hammers in the game
Win an extra race without collecting a chilli
Find and activate all demon portals
Finish the game on „Nightmare“ difficulty