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