Here is the full list of all 25 Azure Striker Gunvolt 2 achievements.
Complete all of the Achievements
Listened to all of the songs.
Saw the hidden epilogue.
Cleared The Garden 3 as Gunvolt with a rank of S or higher.
Cleared Mysterious Manor as Gunvolt with a rank of S or higher.
Cleared Downtown as Gunvolt with a rank of S or higher.
Cleared The Garden 1 as Copen with a rank of S or higher.
Cleared Sewers as Copen with a rank of S or higher.
Cleared Frozen City as Copen with a rank of S or higher.
Cleared Highway as Copen with a rank of S or higher.
Cleared Isle of Dreams as Copen with a rank of S or higher.
Cleared Babel as Copen with a rank of S or higher.
Cleared Downtown as Copen with a rank of S or higher.
Finished the game and got the True Ending as Copen.
Finished the game and got the True Ending as Gunvolt.
Cleared The Garden 2 as Gunvolt with a rank of S or higher.
Cleared The Garden 1 as Gunvolt with a rank of S or higher.
Cleared Highway as Gunvolt with a rank of S or higher.
Cleared Frozen City as Gunvolt with a rank of S or higher.
Cleared Data Facility as Gunvolt with a rank of S or higher.
Cleared Sewers as Gunvolt with a rank of S or higher.
Cleared The Garden 2 as Copen with a rank of S or higher.
Cleared The Garden 3 as Copen with a rank of S or higher.
Watched the cutscene where Mytyl gets kidnapped.
Cleared Seraph Interior as Gunvolt with a rank of S or higher.