Here is the full list of all 55 Omega Quintet achievements.
Finished Episode 7.
Finished Episode 5.
Finished Episode 6.
Used group defense 100 times.
Defeated an enemy with an Extra Chain.
Maximum damage exceeded 100,000.
Maximum hit count exceeded 300.
Maximum hit count exceeded 200.
Defeated 1,000 enemies.
Cleared the Training Facility [1st Floor].
Maximum hit count exceeded 100.
Fulfilled a Request.
Activated Live Concert Mode.
Activated Voltage Gauge Level 5 during Live Concert Mode.
Finished Episode 4.
Generated a Follow Bonus.
Maximum damage exceeded 10,000.
Finished Episode 3.
Defeated an enemy with a Harmonic Chain.
Generated a Link Bonus.
Used pair defense 100 times.
Finished Episode 2.
Succeeded in executing Overkill.
Defeated 100 enemies.
Hunted 10 MADs with Takt's pursuit.
Used the PVS.
Finished Episode 1.
Defeated an enemy with a Special Skill.
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.
Fulfilled 100 Requests.
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.