Making a good villain isn't too different from making a good hero. People are defined through their actions. If you preach good but don't do it, you're a hypocrite. If you act all tough and dangerous, but nurse back the baby bird to health, you're a big softie in disguise. A hero could be afraid of being alone, so determined to protect his childhood friend when (s)he goes out into the dangerous wild, putting his own life at stake. A villain with the same desire, could lock up said childhood friend in his lair so they won't ever have to even face danger. One method to fight this fear is considered admirable, the other plain creepy. Yet they work from the same core desire. What makes a villain hate-able then? A dissonance the viewer experiences between the villain's desire (can be related to) and ways to achieve this desire (can not be related to.)