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