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