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