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