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