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