I am a major player of AC, but I don't play MP games, and I am also a major achievement earner, yet in order to get 100% Achievements, you have to play MP. In my opinion, the player should have the option of earning online achievements, and just have those achievements not be added to the list. I would be happy with out the MP achievements, but it doesn't look good on my achievement completion. Have it state that the player choose not to do MP but has achieved all other achievements.