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