Here is the full list of all 41 SG/ZH: School Girl/Zombie Hunter achievements.
You achieved everything!
Obtain all weapons.
Obtain Rank SSS in all offline missions on all difficulty settings.
Clear all offline missions on all difficulty settings.
Defeat a total of 10,000 enemies.
Obtain all oufits.
Obtain all shoes.
Defeat all Charons and then clear any mission.
Defeat Ren by yourself in an offline mission or hosted online mission.
Defeat a total of 5,000 enemies.
See the ending by beating the game.
Clear Chapter 5.
Use an Underwear Trap for the first time.
Clear Chapter 4.
Defeat Die Jaeger by yourself in an offline mission or hosted online mission.
Obtain 50% of all weapons.
Clear Chapter 3.
Clear a Boss mission for the first time.
Obtain shoes for the first time.
Clear Chapter 2.
Defeat a total of 1,000 enemies.
Clear a Timed Survival mission for the first time.
Clear a Fetch mission for the first time.
Use a Club Attack 10 times in a single mission.
Clear Chapter 1.
Undress 3 people during a single mission.
Use Mayaya for the first time and clear a mission.
Defeat all Charons in one mission, then clear the mission.
Use Rei for the first time and clear a mission.
Defeat a total of 100 enemies.
Use Enami for the first time and clear a mission.
Use Risa for the first time and clear a mission.
Use a Club Attack for the first time.
Obtain an oufit for the first time.
Clear a Destination mission for the first time.
Defeat Charon for the first time and then clear a mission.
Obtain a new weapon for the first time.
Use Sayuri for the first time and clear a mission.
Clear a mission for the first time.
Undress for the first time.
Attack a zombie's weak point for the first time.