Mine that was crazy aggressive was a red sex link and an ancona. I have read that red sex links can be like that. I also have been told by many that rhode island reds don't mix well with really docile breeds like buffs, and ameraucanas. My grampa had rhode islands and they were aggressive.
Exactly...Reds dont always get along with other colours of chickens. Red birds are more aggressive.
I sold all my red hens.