There are plenty of posts on this site about aggressive roosters and how to deal with them, a quick search should bring up lots of ideas.
Most can be hard to fix if the rooster is older. I would use a tool like a broom, plastic rake or fishing net, my favorite to block his attacks and drive him back. Than I would go on the offensive every time I see him, making sure he keeps his distance, at least 10 feet and preferably runs when he sees you coming.
Keep at it and he may change his mind. If he doesn't after a few weeks to months he would be culled by me.
Roosters are best not being friendly which can often lead to aggression as a rooster always wants to move up in his position in life.