If your cock or cockerel is aggressive to male or female coop mates, see the simple remedy at the end of this article
There are several things one can do when a cock or cockerel is too aggressive. I disagree with those who kill all their aggressive males. The aggression is a consequence of characteristics male chickens need. As Fred P. Jeffrey says in Bantam Chickens:
"What is wanted is a 'showoff' a male that struts around, fears nothing, and likes to strike a pose. A listless male, even though he is tame, should not be used as a breeder."
"Breeding for an ideal temperament is a complicated business. For example, one of the extreme forms of 'showing off' is truculence where the male, and sometimes female, attacks the caretaker."
What I do for an aggressive male is to pick him up, tuck him under my arm, and carry him around. We do all my poultry chores together. We clean the coop together, we fill the feed containers together, and we clean the waterers together. I might have to carry the little guy around for a week or more. It is often a struggle to stop myself from popping the little guy when he pecks or grabs me. I find that showing aggression just makes things worse. Carrying the bird around shows I am so very big I don't even have to fight I just win.
Sometimes I invent a tune to sing when I pick him up for his daily ride. One of our best white bearded Silkie breeders is Ducky. Ducky was magical in his attacks. You won't see Ducky until the moment you turn your back to leave the coop. That's the very moment Ducky will appear out of nowhere and grab the back of your leg. Ducky is now a perfect gentleman. When Ducky hears me sing his special tune he scoots away and wobbles his lower beak up and down. He is so very cute.
Another method I have successfully used is to hold the aggressive male face toward me with one hand on either of his sides. I slowly lower him to an about waist high surface. If he struggles and squirms when his feet touch, I slowly and gently raise him and start over. He might never touch the surface without squirming for the first week. Each session is never longer than a minute or two. Finally he will support his own weight on the surface without squirming.
In the next stage of training, I slowly release my grip. If he struggles, I grip again. If he struggles a lot, I raise him and start over. He will eventually stand with my hands on either side of him but not touching him. The final stage trains him to stay put as I move my hands away.
Other people carry a spray bottle and adjust it to a solid stream. They squirt the aggressive males when they attack. I think this uses the same principal as do my methods. You win the battle without actually engaging in battle. You are too invincible to even consider fighting. He doesn't get into the habit of fighting; he gets into the habit of having lost before battle begins.