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