I've been lucky as I've only had 1 mean roo that couldn't be changed. The other one I had changed his mind about attacking humans when I held him upside down until he calmed down and then turned him loose again. He he attacked again, i would pick him up and hold him upside down until he relaxed. It only took a couple of times before he decided to back down to humans. He would still attack other animals if he thought they were going to hurt his girls, so it didn't break his spirit, it just taught him who the top chicken is.