Mby give this boss and opportunity to calm down so u can after some time try to cc right again? I think now he wont calm from his rage, if u make mistake. Its so time consuming if u make mistake on him and cant have 2nd shot for it. Usually i got it right now, but like now i did mistake stiff for stun or so >:). There goes all time for naught again.

forfeit the quest and retry

IF you are talking about the Kagtum that has 2 forms.  When he's in his weaker human form you just attack like normal.  When he goes in his hulked out form, dont attack don't even have your weapons out.  You just run around the Arena until he gets bored.  You don't need to kill the hulked out form.  After the Hulked out form exhausts all it's stamina it stops chasing and goes back to humanish form.