Here is the full list of all 47 ECHO achievements.
Look at yourself in the mirror excessively
Traverse infinity for a while
Line up and shoot 6 Echoes with a single shot
Finish the game on any difficulty
Take out a Hyper Echo
Reach Chapter VI
Get Foster back
Use Area Scan 20 times
Get 4 additional Cell capacity slots
Reach Chapter V
Shoot 200 Echoes
Take out 47 Echoes with the stealth takedown
Throw 20 Crystal Balls
Collect a Voice by having an Echo strike it
Collect 25 Voices
Tag 100 Echoes
Play the whole piano piece during a blackout
Get 2 additional Cell capacity slot
Push 50 Echoes
Reach Chapter IV
Kill 10 Echoes with Crystal Balls
Pick up 50 Suns
Have Echoes know how to sprint, vault, use doors and walk in water at the same time
Collect 10 Voices
Get an additional Cell capacity slot
Push an Echo over a railing
Eat 20 pieces of fruit
Eat 5 pieces of fruit during a single blackout
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
Push 5 Echoes at once with the Riot Gun
Distract 5 Echoes at once with one Crystal Ball
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
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