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