Well, we're talking about a villain who, as a schoolchild, inquired about splitting his soul, not once, but six times.
He was capable of great harm and deceit even at the orphanage where he was first introduced to the wizarding world.
He rose from orphaned boy to dark lord, with his only real gift being that he was a parselmouth. Other than that, it was his drive for power, his lust for it, that made him ascend. He was capable of being a "perfect" student to all those that saw him, but inside he was already Lord Voldemort, hating his Muggle father's name and already subscribing to the racist notion of pure blood wizards being superior to half-blood or "Mudbloods". He was very much like Hitler in this. Hitler believed that blonde haired, blue eyed white men and women were the superior race, despite being a dark haired individual. Voldemort was a half-blood, yet only allowed pure bloods to be his Death Eaters.
I could go on and on. I was very impressed with the villain she created.
But, as you say, it is a matter of opinion.