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