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