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