Here is the full list of all 30 Disgaea PC achievements.
Completed Final Episode of Etna Mode "Chronicles of Etnarnia"
Completed Ep. 1 of Etna Mode "Super Dimensional Etna"
Defeated all EX bosses!
Obtained the Hyperdrive!
Defeated the Extra Boss "Item God 2"
Dealt 10,000,000 Damage!
Performed 10 transmigrations
Defeated the Extra Boss "Item God"
Defeated the Extra Boss "Item King"
Defeated the Extra Boss "Baal"
Dealt 100,000 Damage!
Defeated the Extra Boss "Marjoly"
Defeated the Extra Boss "Priere"
Obtained 10,000,000 HL at the end of battle
Cleared Extra Stages "Cave of Ordeal"
Obtained Total LV 10,000
Obtained Total LV 1,000
Obtained Total LV 5,000
Completed Final Episode "What Lies Beyond the Battle"
Obtained Total LV 100
Killed 1,000 enemies!
Completed Ep. 10 "Angels, Demons, and Humans"
Obtained 1,000,000 HL
Performed your first transmigration
Killed 500 enemies!
Completed Ep. 5 "Etna's Secret"
Obtained the Dream Hand!
Defeated the Extra Boss "Item General"
Completed Ep. 1 "Prince of the Netherworld"
Killed 100 enemies!