Here is the full list of all 55 Disgaea 2 PC achievements.
Defeated all EX bosses!
Dealt 100,000,000 damage!
Defeated the Extra Boss "Pringer X Go"
Saw the Tink ending
Performed your first Peta spell
Obtained the Yoshitsuna!
Dealt 10,000,000 damage!
Reincarnated 10 times
Obtained LV 9,999!
Cleared Extra Stage "Evil Academy Special Class!"
Entered the Land of Carnage for the first time
Cleared Extra Stages "Cave of Ordeals"
Unleashed Magichange 2
Defeated the Extra Boss "Item God"
Completed Ch. 4 of Axel's Story "The Dark Hero!"
Completed Ch. 1 of Axel's Story "The Evil Rangers"
Performed your first Magichange
Saw Bad Ending 2
Saw Bad Ending 1
Cleared 100% of the Dark World stages
Cleared 50% of the Dark World stages
Cleared 20% of the Dark World stages
Defeated the Extra Boss "Baal"
Defeated the Extra Boss "Zetta"
Defeated the Extra Boss "Prism Ranger"
Defeated the Extra Boss "Flonne"
Defeated the Extra Boss "Laharl"
Saw the Axel ending
Dealt 1,000,000 damage!
Saw the Laharl ending
Saw the Etna ending
Defeated the Extra Boss "Marjoly"
Earned 10,000,000 HL from a single battle
Obtained Total LV 10,000
Defeated the Extra Boss "Protype Kurtis"
Defeated the Extra Boss "Kurtis"
Dealt 100,000 damage!
Obtained LV 1,000!
Obtained 99 felonies
Defeated the Extra Boss "Priere"
Defeated your first pirate in the Item World
Obtained Total LV 5,000
Unlocked the Dark World
Defeated the Extra Boss "Mid-Boss"
Defeated the Extra Boss "Asagi"
Obtained LV 100!
Completed Final Chapter "The Truth"
Obtained 1,000,000 HL!
Completed Ch. 10 "The Two Ninjas"
Killed 1,000 enemies!
Completed Ch. 5 "The Promise"
Performed your first reincarnation
Attended your first trial in the Item World
Killed 100 enemies!
Completed Ch. 1 "The Overlord's Daughter"