Full list of all 26 Kao the Kangaroo achievements worth 1,620 gamerscore. It takes around 8-10 hours to unlock all of the achievements in the base game.
The base game contains 15 achievements worth 1,000 Gamerscore, and there is 1 DLC pack containing 11 achievements worth 620 Gamerscore.
Finish the game
Complete the tutorial with Walt
Find and defeat Terror
Defeat Jayabaya
Defeat The Oldest One
Beat The Eternal Warrior
Collect the KAO letters on all levels
Unlock all extra heart slots
Collect all the Kaopedia entries about Foes
Collect all the runes
Defeat one of the bosses without receiving any damage
Find and complete all of the Eternal Wells
Have 20 lives in total
Defeat five enemies at once with a finisher
Wear an outfit from Kao 3
Complete Waterfall Islands (Easy Mode)
Complete Waterfall Islands (Hard Mode)
Complete Volcano Peaks (Easy Mode)
Complete Volcano Peaks (Hard Mode)
Complete Forsaken Monastery (Easy Mode)
Complete Forsaken Monastery (Hard Mode)
Complete Twisted Hideout (Easy Mode)
Complete Twisted Hideout (Hard Mode)
Defeat the Crab King
Collect every diamond in the DLC
Find the Frozen Pirate from Kao 2