What to do with aggressive rooster?

[Luffpuff]

If you are interested in trying to rehabilitate him, here is a great article. On the bottom there are tips and routines to help train an aggressive rooster and take the Alpha position in the flock.

http://chickenrunrescue.org/filter/Care-and-Rehabilitation/Rooster-Behavior

 

[cottontail farm]

I agree with you 1000% that the only ethical thing to do is cull the rooster. The most humane way is to do it yourself on your property so you're not stressing him.
I suggest you look up the broomstick method. When I cull chickens this is how I do it and it's going to make it easier on both of you. Take him off the roost at night when he's asleep and immediately turn him upside down. He's going to have about 2 seconds between waking up and thinking huh? and going limp. Ask anyone here: a chicken looses conciousness almost instantly when upside down. Then broomstick him. It's instant and doing it in the dark will make it so much easier on YOU too as you won't be exposed to it as much as you would during the day.
You say you hunt: a 22 is another good alternative.