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