Multiplayer isn't a requirement to get all 1000 points.
Mass Effect 3 is one of the most highly anticipated games of 2012, but it hasn’t been without its share of controversy or concern amongst fans. There’s the confusing ability to play the game in three different modes that range from all action to all story. There’s been the uproar over the multiplayer DLC slated to be packaged with the upcoming release of action figures, and of course there’s been the concern over the inclusion of multiplayer in general. While the multiplayer in Mass Effect 3 can impact your progression in the single player game, it’s not mandatory, and the achievements for the game reflect that.