Here is the full list of all 9 Maui achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Enter the Halau for the first time
Plant your first taro
Fulfill your kuleana
Gain the favor of Lono
Gain the favor of Kanaloa
Find a strange island
Gain the favor of Ku
Gain the favor of Kane
Defeat your first enemy