Here is the full list of all 31 Aegis Defenders achievements.
Discovered Aegis
Collected 5 Relics
Killed 100 Enemies
Bart Joined the Party
Clu Joined the Party
Complete Area 1
Complete Area 2
Complete Area 3
Complete Area 4
Complete Area 5
Complete Area 6
Kaiim Joined the Party
Zula Joined the Party
Collected 15 Relics
Collected All the Relics
Killed 200 Enemies
Killed 300 Enemies
Defeat the (KS) Breath Dragon
Defeat the Zanoh
Defeat the MadXArmor
Complete Game on Hard Difficulty
Complete Game on Insane Difficulty
Purchase 5 items
Purchase 15 items
Purchase all items
Earn 50 RP from Dialog Choices
Complete an entire area without dying
Complete the game without dying
Obtained The Blood of A God
Rescued Shreya
Found Kobo and the Clarent