Usually the truly shit shows no one in the right mind would defend just aren't talked about because they're just awful.
Regardless of how you may think of the usual dead horses (SEED Destiny, IBO, ZZ, Aldnoah Zero, Valvrave, Cross Ange, etc.), they all have their strengths and people will argue, which is why they're good as bait.
Something truly reviled by all would have to be an abject failure on both production and creative levels, which is actually quite rare.
Maybe something like the EX-ARM anime? I've not seen anyone try to defend that yet.