Can a poorly done second degree ruin one's academic record?
Yes.

I think it is pretty obvious that if you provide the transcript for your second degree, a poor performance harms your chances.  This provides relevant information about your academic ability and/or work ethic, which a graduate program would consider.  It might even be weighed more heavily than your first degree, since it is more recent (and in a relevant subject to your planned masters').

So the question becomes can you just not tell graduate programs about your second degree?  I don't think this is a viable option.  A graduate program will expect you to submit information about all previous studies.  Not submitting a transcript for a second batchelor's degree will most likely be breaking their rules.  You would likely have to be deceptive in any application, interviews, and discussions with the potential graduate institution.  I think this is just wrong, but even if you don't have any moral qualms about it, you are placing yourself in a very bad position.  There is a chance you could get away with it, but you also might get caught, and that would have serious consequences.