Dollhouse. Not because of any intrinsic problem with any of the ideas or plots, given the shows premis they all made sense, but because they all had to be crammed into the final 3 shows and it all seemed extremely rushed consequently.
It wasn't perfect (Eliza Dushku should have been a doll, but Dichen Lachman should have been Echo), but the curse of Fox (and, to be fair, a convoluted ongoing arc) got it cancelled and many great ideas were squeezed into 3 hours.
It wasn't perfect (Eliza Dushku should have been a doll, but Dichen Lachman should have been Echo), but the curse of Fox (and, to be fair, a convoluted ongoing arc) got it cancelled and many great ideas were squeezed into 3 hours.