My own personal achievement in Dragon Age II is getting all my companions to join me in the endgame sequence of Dragon Age II, mostly siding with the mages and playing as a mage Hawke. I pushed Aveline's, Isabela's, Varric's, Fenris', and Anders' friendship levels to maximum. Aveline and Varric weren't much of a problem given that I was playing my mage Hawke as a paragon, but Isabela required some work given that I didn't want her to permanently depart by the time of the Act II closing quest. Fenris was real difficult to get his friendship up given his apparent dislike for mages (I was pro-mage) and I didn't include him much in quests, but by the time I got him the Blade of Mercy and pushed his friendship level up to maximum by accepting the Alone quest and not giving him back to Danarius, my Hawke told him not to kill his sister and I suffered no drop in friendship. Also I had Carver join the Grey Wardens during my playthrough of mage Hawke and didn't kill Thrask in order to let Grace depart in secret, so he survived into the endgame as well. Merrill's friendship level was one I didn't bother trying to increase since she would side with the mages anyway. The only thing I don't have is the Exiled Prince DLC character Sebastian, which would force me to either have him leave the party altogether if I chose to spare Anders or have Anders killed in order to keep Sebastian in the endgame.