What makes a really good villain?

Identity and belonging - two strong words - running through my mind as I am waiting outside the Elephant House in Edinburgh waiting for a friend for a coffee.  I suppose I have always been interested in identity, but it is especially strong due to the fact that I am super fan of the television programme "Who do you think you are", the hit BBC show about exploring people's family tree.

"Sometimes I wonder who I am and how much of me is defined by my ancestry, and if the figures from my tree are shaping me, how do I ensure that I don't lose me whilst being a range of characters for other people." 

If there is an answer to the above thought, I don't know whether we will ever find out.  When you start working through the ghosts in your branches, you start to understand that there are character traits that wonder down the generations and it isn't explainable, because at the end of the day, they may be blood but they are strangers to you and you cannot possible understand their lives and actions.

You are probably wondering what has this got to do with writing? Characters and character development. For me, characterisation is key to my novel and one of the problems (yes, there is more than one) is that my villain, in parts, comes over as a cupboard cutout, which isn't good.

If you are writing any story, it is important that each of the characters has depth and meaning, and although I think I know my villain inside out, I think that I have always written it the novel inside the head of my main characters, and in her eyes, she doesn't really like him.

For a writer, it is easier to write the characters which are nearest to yourself and it takes more vulnerability to write the ones that you really don't akin yourself to. But for my novel to work, my villain has to come across as a real person and there has to be depth to why he acts in the manner he does. I think about the villains that I have enjoyed reading, they have always had the same depth as the hero, and sometimes, the people you see as villains are the heros for other people.

I wonder what make a really good villain in your eyes?