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