Hi JakRat, I know EXACTLY what you mean about MEAN! I have one hen who is just plain nasty. We have tried everything with her, she has heaps of food, space,entertainment, and lots of grass to range on, but she will always seek out one of the other chickens and 'bully' it into moving or giving up whatever it is eating. She has also progressed to feather plucking and eating, and has made a horrible mess of one of my sweet sussex girls. She has also started to crow sometimes, purely to assert dominance.
I have concluded that like people, some chickens are just plain nasty. This girl also dislikes my children and runs a mile sqwaking if anyone goes near her. All of my girls have been raised together, and she is the only one that is not a lap chook, and is vicious to the others. BTW she is a black Australorp (usually considered a docile breed...). I have decided to rehome her, preferably to someone with a rooster to keep her in line, and I will explain her faults when I do so. I initially felt bad about 'giving up' on her, but after what she did to my sussex girls, totally unprovoked, I consider her lucky if she finds herself in a new home rather than a soup pot!