I've had to pen a bully or two through the years. Usually I can pen up a bully in large wired type dog kennel for a week, and then re-introduce, and things go fine then, or re-pen it up for another few days. After the second round of being penned up, even one of my worst bullies got the message. BUT there are many on here that have a bully that simply can't be broken from bullying. That's when it's time to get rid of the bully. Sometimes it's a hard choice, but the resulting peace in the flock is worth the choice. It's always so much more pleasant to have a peaceful flock.