I agree with the others that neutering may help.

There is also Feliway plug-ins and sprays which help some cats to calm down, as well as "rescue remedy" which is a natural medication. Otherwise your vet may be able to prescribe something to calm the aggressive cat?

I also have two cats who fight. I try to keep their claws clipped too so they don't hurt each other with every argument.

Best of luck, and please keep us updated