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