Here is the full list of all 52 Operation STEEL achievements.
Complete Level E
Destroy Taurus
Complete Level G
Destroy Virgo
Complete Level D
Destroy Pisces
Complete Level C
Destroy Aquarius
Destroy Leo
Complete Level B
Destroy Gemini
Complete Level A
Destroy Cancer
Complete Level F
Complete Level H
Complete Level I
Complete Level J
Complete Level K
Complete Level L
Complete Level M
Complete Level N
Complete Level O
Complete Level P
Complete Level Q
Complete Level R
Complete Level S
Complete Level T
Complete Level X
Complete Time Attack
Complete Boss Rush
Destroy Scorpio
Destroy Capricorn
Destroy Aries
Destroy Sagittarius
Destroy Libra
Destroy Dragon
Destroy Timeron
Destroy Sol
Complete the tutorial
Complete the starmap
Complete Hard Mode
Score 200,000 or more in Time Attack
Save the Galaxy
Complete Hard Mode 2
Complete Hard Mode 3
Complete Hard Mode 4
Complete Hard Mode 5
Complete Hard Mode 6
Complete Hard Mode 7
Complete Hard Mode 8
Complete Hard Mode 9
Complete Hard Mode 10