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