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