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