A man far better at writing than I am shared this article on magicalwords.net. Everyone, please meet Jim Butcher, and his article on “How to build a Villain”: http://www.magicalwords.net/really-i-mean-it/how-to-build-a-villain-by-jim-butcher/
To those of us who are really just getting into the writing game and want advice on how to create characters that you can love and hate, I highly suggest this read.
Butcher also then spend the rest of the afternoon answering questions other readers had on the writing-craft. So more than just making a villain, there are answers to all sorts of questions we as authors will found interesting and helpful.