Respect the Maledict (Doom 3: Resurrection of Evil)
If you thought the Cyberdemon was the biggest Doom baddie, you haven't seen anything yet. The Maledict is much faster and far more cunning than Cybey ever was (has a lot more health too). Unsurprisingly, he also has the ability to send Lost Souls and other annoying enemies after you when facing him.
Heh. Didn't think about that, but I guess you're right. Even if he doesn't though, I'll still appreciate him for what he was and accept that he wasn't in a sequel, like I did with Eckhart's Two-Face from TDK.
I guess the likelihood of Maledict being in Doom 4 though is pretty much the same as the Cyberdemon's.