No you cannot sell it.
The problem is that Valve does not abide by the law, because in the UK we have the right to return something that is not fit for purpose and that perfectly describes, Black Op's 2 but you cannot return it, and I did that after a month of Medal Of Honor Warfighter being released.
Software is not exempt and neither is digitally distributed material.
The other problem is that you say you have only tried it twice, but the problem you will have is if someone is stupid enough to buy your steam account is that you could have cheated twice and be getting banned but they won't know that.
Like the rest of us you are sh** of luck and just have to move on to a more supported and all round better game aka COD 4.