In a very roundabout way, Abigail Mitchell. Not for being creepy, but just the opposite, for being one of those "loveable eccentric" Ruth Gordon characters. Which is a little disturbing, since she just committed a vigilante type killing, and (along with Adrian Carsini) one of the most drawn-out killings. And on top of that, you never find out for sure whether the victim had done anything to deserve it! (I know some of you are pretty certain that Edmund killed Phyllis, but some of us have real doubts about it.)