I had a nasty hen my first year. Plucked and broke feathers on 2 other hens, and then pecked at the bloody spots. She also terrorized the Barred Rocks I tried to integrate. I tried to discipline her by putting her in chicken jail a few times. I even put little jackets I made out of the legs of jeans on the injured hens, but she just went for their tail feathers. I ended up rehoming her, because I did not feel capable of fixing the issue due to lack of experience.
The guy who took her and her same breed bullied sisters (I let him know the problem before giving her over) was able to rehabilitate her rather quickly, I was surprised and a little sheepish. Her sisters grew all their feathers back, and all was good. Turns out, she just needed more space and free range environment. From what I understand, some aggressive hens are easier to break than others, and it's a matter of figuring out what they need. And if all else fails, there's always chicken dinner.