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