Gosh, I wish I could find the post...someone on here uses this approach in EXTREME cases, which it sure sounds like yours is.
He removed the roo to a small dog kennel, and puts it in a place that is dark and without outside contact from humans or other critters for 24 hours. COMPLETELY dark, and he's alone. This person does not feed or water for 24 hours (which I personally find leaning toward inhumane, but if the option is to cull a perfectly healthy rooster, I guess it's an option to try). After the 24 hours, give food and water...have your DD or wife do this, so the roo understand that his sustenance comes from them. I BELIEVE the roos is still in the dark at htis point. After several days (sorry, I don't recall how many), move him to a larger kennel or crate or whatever, and move him to the light, but still no contact with others. Several more days...then, add a hen into the crate for him. Again, you're showing him that YOU are in control (or DD or DW). After several more days, try allowing him out for a short time, then catch and return him to the crate. Return him to the crate in a short time, assuming he'll be so happy to be out, the last thing on his mind will be flogging a human. THen put him right back in the crate BEFORE he thinks in that direction. Slowly SLOWLY prolong the time you allow him out.
I've never done this, but it supposedly works on the most wicked roos. I wish you the very best. Please, please be careful NOT to kick your roo. I did this once in a self-defending way when I was being literally attacked by my first roo, and I broke his bottom beak off. I'm ashamed to admit that, but if it makes someone else think twice about kicking a roo, my embarrassment is worth it.