Like a few have said, a dash of multiplayer is one thing. This is quite a bit more than a dash as far as achievements are concerned. And what's worse is that the single player portion of the game is reviewing very well but everyone agrees the mulyiplayer is bad, so we hate it more before we even play it. Fifty hours is a decent amount of time for a single player game nowadays, but fifty hours on a bad multiplayer component? Keep it.
If they were going to force multiplayer into a Tomb Raider game they should have atleast gone with co-op maps. Atleast then they could have made some clever two-player puzzles and had a shot at it being decent. I feel comfortable speaking for everybody when I say: Nobody wanted this!