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