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