That looks terrible! You cannot overlook such an aggressive animal. It would be cruel on the victim/s. You could either isolate him (which would make him unhappy) or dispose of him humanely. I'm sorry to say this.
Aw, poor baby. I agree with the others- I would send that roo to freezer camp if he did in fact do it. Just be sure first that he did it, sometimes hens can be aggressive when establishing the pecking order.
So many nice roos out there that need a home there is no reason to keep a mean one, especially when they are mean to the girls. They are suppose to serve and protect
If you haven't already I would clean her up good and spray her with some BlueKote. If you don't the other chickens will be attracted to the blood and injured spots, they will peck at her and hurt her further. The Blue Kote will serve as an antibiotic and cover up the blood/ injured area. This stuff works great and you should always have a can on hand for injuries.
I separated him earlier and gave the girls half a pumpkin. That cheered them up but it doesn't make me feel better. Maybe some ice-cream...
I cleaned up the injured hen and used the bluecoat. She was a good patient and looks much better. She has a blue spot on the side of her and on my hands - LOL
Keeping in mind that he may, depending on his personality, start to pine for company if he's by himself. And yes go for the icecream! It works wonders, like chocolate....