Now Kurata's having been made a villain by his own nature was a unique twist, and I think if that had been used in Zero Two, I would have enjoyed that series much better (though I currently, and will continue to, maintain the viewpoint that the series should have ended with Ken).
Ken was, to quote my friend, "immature and traumatized over his brother's loss" - the perfect fuel for becoming the Kaiser. It was also very nice that Kurata was not "controlled," a syndrome which plagued the past seasons - he was an adult, he was old enough to know if he's doing something wrong, and was acting on his own nature.
And really, looking at Kurata - he's a sadistic, bloodthirsty man who at heart believes what he's doing to be right - it's the same sort of feel that made Yamaki a good villain, only this time around, he didn't come to see his actions as wrongdoings. That, and he was far more of a vicious being.