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