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