When considering a villian's leverage on a protagonist, which is more effective: the character's greatest want or greatest fear? To exploit what the hero wants most drives them to make blind choices and keeps them ultimately responsible for their own decisions. It allows the author to take that one fatal character flaw and draw it out in tragedy. The story, is then, driven, by the protagonist's supreme desire to achieve their goal.
If the villian uses the main character's most basic fear against them, the reader connects on a deeper emotional level, especially if that fear is a universal one driven by the same values and desires humanity shares. It does, however, make for a weaker potential for character growth--a somewhat superificial reactive character that yields a less satisfying read. Yes, the hero ultimately overcomes their greatest fear, but are they as human as they would be had we seen them succumb to the baser desires that drive us all? The mistakes that reveal the most about the human condition?
"The creative power, which bubbles so pleasantly in the beginning of a new book, quiets down after a time, and one goes on more steadily. Doubts creep in. Then one becomes resigned. Determination not to give in, and the sense of an impending shape, keep one at it more than anything." ~Virginia Woolf