Here is the full list of all 55 Omega Quintet achievements.
Finished Episode 7.
Defeated 1,000 enemies.
Maximum damage exceeded 100,000.
Cleared the Training Facility [1st Floor].
Fulfilled 100 Requests.
Finished Episode 6.
Defeated an enemy with a Special Skill.
Defeated an enemy with an Extra Chain.
Maximum hit count exceeded 300.
Maximum hit count exceeded 200.
Finished Episode 5.
Defeated an enemy with a Harmonic Chain.
Fulfilled a Request.
Activated Voltage Gauge Level 5 during Live Concert Mode.
Maximum hit count exceeded 100.
Generated a Link Bonus.
Activated Live Concert Mode.
Maximum damage exceeded 10,000.
Finished Episode 4.
Generated a Follow Bonus.
Finished Episode 3.
Finished Episode 2.
Defeated 100 enemies.
Succeeded in executing Overkill.
Used the PVS.
Finished Episode 1.
Obtained all trophies.
Cleared the Training Facility [5th Floor].
Cleared the Training Facility [6th Floor].
Cleared the Training Facility [7th Floor].
Cleared the Training Facility [8th Floor].
Cleared the Training Facility [9th Floor].
Cleared the Training Facility [10th Floor].
Cleared the Training Facility [11th Floor].
Cleared the Training Facility [12th Floor].
Otoha reached max affection.
Kyouka reached max affection.
Kanadeko reached max affection.
Nene reached max affection.
Aria reached max affection.
Defeated 10,000 enemies.
Finished Episode 8.
Finished Episode 9.
Reached the true ending.
Reached the game's ending.
Hunted 10 MADs with Takt's pursuit.
Used pair defense 100 times.
Used group defense 100 times.
Maximum damage exceeded 1 million.
Reached the true ending in Advanced mode.
Approval rating exceeded 1 billion.
Completed archives.
Maximized proficiency in all 5 Mic types with any one character.
Finished all Quests.
Defeated Double X.