Ultimately, the last time I broke up with him was for the same reason as all of the other times: he was not a kind person. His brilliance is unquestioned, and he was frequently right in whatever point he was making, but without kindness and compassion it was useless to me in a relationship. At the end of the day, it didn't matter whether I was being fair or not; once I acknowledged to myself that I couldn't give space to a part of his nature, and that it was a part of his nature that he couldn't alter as much as I needed him to, or even as much as he said he wanted to, it was over. But I certainly gave it my best before I threw in the towel.
That was well said. I have found myself in a situation so similar that it could have been the same man. I didn't have the clarity to see it the way you did. I thought I was in love and I let it go on for far too long. He was so many wonderful things, I just kept explaining away his cruelty because he had so many other desirable traits.