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