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