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