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