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If he is agressive to other roosters: Some breed is more game than others. However, in a yard, normally 1 rooster will be dominant to a role of leader. Once they recognize he is the leader, they will fear him and the yard will be peaceful again. Just watch out so he won't hurt others too bad. If he continues to beat up his fellow, then separate him.
If he is agressive to hens .. this is normal for young rooster to start gaining his maturity. They will soon become a flock for him. Just watch out to make sure he won't beat up the hens and other males.
If he is agressive to people.... some of them gets mean during the moulting. Don't touch them as this hurts them and they get meaner. Also, don't catch their hens in front of them as they will try to protect their hens. Once the moulting is over, they will either become normal, or they will be permanently mean ... in the second case, pen him or eat him.