Here is the full list of all 24 ALLTYNEX Second achievements.
1 credit cleared with Type-B Craft
1 credit cleared at Normal or higher difficulty with return shot mode on
Return Shot Mode unlocked
1 credit cleared
Score Over 10,000,000
Shoot down 10,000 enemies
Type-B Craft rolled out
Visitor Defeated
Mission accomplished
Ophiuchus Husk Defeated
Alacran Defeated
Score Over 6,000,000
Ajattara Defeated
Adoni Defeated
Zoldyzant Defeated
Score Over 3,000,000
Slash an enemy with a 16x multiplier
Encounter the Omega Javelin
Obtain 25,600 point combo bonuses 10 times in a row
Shoot down 1,000 enemies
Score Over 1,000,000
Aseliel Defeated
Shoot down 100 enemies
First campaign