Here is the full list of all 47 ECHO achievements.
Finish the game on Ultra Hard
Collect all Voices
Pick up every orb in every caste level
Have Echoes play the harp and piano at the same time.
Collect 100 Voices
Complete the fifth Verse
Kill 3 Echoes by shooting a Sun
Complete the fourth Verse
Look at yourself in the mirror excessively
Eat 5 pieces of fruit during a single blackout
Traverse infinity for a while
Have Echoes know how to sprint, vault, use doors and walk in water at the same time
Push 5 Echoes at once with the Riot Gun
Complete the third Verse
Throw 20 Crystal Balls
Shout and get the attention of 8 Echoes at once
Complete the second Verse
Collect 50 Voices
Distract 5 Echoes at once with one Crystal Ball
Play the whole piano piece during a blackout
Make a 2 cell energy drop during a blackout
Collect a Voice by having an Echo strike it
Complete the first Verse
Shoot 200 Echoes
Tag 100 Echoes
Finish the game on any difficulty
Take out a Hyper Echo
Reach Chapter VI
Get 4 additional Cell capacity slots
Collect 25 Voices
Get Foster back
Eat 20 pieces of fruit
Take out 47 Echoes with the stealth takedown
Reach Chapter V
Push an Echo over a railing
Push 50 Echoes
Get 2 additional Cell capacity slot
Pick up 50 Suns
Reach Chapter IV
Kill 10 Echoes with Crystal Balls
Collect 10 Voices
Use Area Scan 20 times
Get an additional Cell capacity slot
Reach Chapter III
Line up and shoot 3 Echoes with a single shot
Line up and shoot 6 Echoes with a single shot
Activate the palace