I liked Warren. He was an insecure little man who, rather than trying so hard to make it the "right" way like even our vamp boys eventually do, instead tried to threaten and coerce people into making things easy for him -- the slimy way. It wasn't just that did wrong. It was the selfish, weasley way in which he did wrong that made him great. He had no loyalty, no human connection. Heck, even Dru had loyalty! He was sub-human. The reason that Warren lost his humanity, (perhaps his soul?) though, was because he was isolated and inept and insecure. He was a perfect villain for season 6: someone who faced his inner demons, like the scoobies did, but lost.