Mutant Love
Have Cyclops in your party at the start of Muderwold. You'll talk to Jean and get the achievement. Fleeting Allies
Have Magneto in your party before you enter the Mephisto's realm level. You'll chat with Prof. X and get the achievement. Wrong Claws
Have Sabertooth in your party after the opening level on the Shi'ar ship. When you talk to Gladiator, he'll mistake Sabertooth for Wolverine and you'll get the acievement. Doppelganger
Have Doom in your party for the final boss battle. Doom chats with himself right away and you get the achivement.