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