Um guia para quem estuda Inglês Online
This is what I found in Longman dictionary:
hate - an angry unpleasant feeling that someone has when they hate someone and want to harm them ￚsynonym hatred
hatred - an angry feeling of extreme dislike for someone or something
I don't think there is any difference between them since they are synonyms, except may be the word 'extreme', as mentioned before by other members of the forum.