Here is the full list of all 42 GUILTY GEAR 2 -OVERTURE- achievements.
Finish mission #5 "Gaze of the Chronicle"
Open one hidden treasure chest
Finished mission #2 "The Alarm Always Rings Unexpectedly"
Finish mission #0 "Noise"
Finish Campaign Mode
Finish Campaign Mode on Hard
Finish all default Free Missions using any master
Finish one default Free Mission with all masters
Finish half of the default Free Missions using all masters
Finish all of the default Free Missions using all masters
Finish all of the default Free Missions using Sol
Finish all of the default Free Missions using Sin
Finish all of the default Free Missions using Izuna
Finish all of the default Free Missions using Dr. Paradigm
Finish all of the default Free Missions using Valentine
Finish one match online
Finish one Tag Match (2vs2)
Win 3 times with Sol online
Win 3 times with Sin online
Win 3 times with Izuna online
Win 3 times with Dr. Paradigm online
Win 3 times with Valentine online
Win 5 times online
Win 20 times online
Finish mission #15 "Roaring Compass"
Finish mission #17 "Demon"
Finish mission #18 "The Birth of a Girl"
Unlock Ky Kiske
Open half of the hidden treasure chests
Open all of the hidden treasure chests
Get an S rank in all Campaign missions on Normal or higher
Finish all of the default Free Missions using Ky
Kill 100 enemy capture units with your master in one match in battle
Kill 20 enemy servants with your master in one match in battle
Use any type of item 30 times in one match in battle
Open 5 treasure chests in one match in battle
Slip on a Banana in battle
Win 3 times with Ky online
Destroy the enemy masterghost on the first round of a online match
Lose 3 times online
Finish all of the default Free Missions using Raven
Win 3 times with Raven online