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