Actually, to a greater extent it's been the Warren Ellis Constantine- I only know the Gaiman version from the Books of Magic original miniseries, and I haven't actually touched my copy of that in months on end. I have periodically pulled out my copy of the Haunted TPB and reread it. Granted, John is more of a bastard there than in what I've written so far, but Ellis' bastard is less generically horrible and more horrible towards people who really bloody deserve it.

But you're quite right; he needs to be more horrible, and soon. Beyond merely using an Unforgivable in front of the students, which I believe I'll have him do next chapter. I shall ponder this.