Definitely too many. Villains, especially voiced by gifted character actors, often are so much more sumptuous to behold and listen to than your erstwhile bland-faced protagonists. That's why the Transcendent One, Sarevok, and Irenicus were so memorable. Not because they were particularly unique adversaries or baddies as it were, but because they were voiced by the great Tony Jay, Kevin M. Richardson, and David Warner, respectively.
I think my vote will go to Karras from Thief: The Metal Age. In a fight, this guy wouldn't stand a chance. A sallow, sickly, sour-faced priest with an unfortunate lisp that sounds like Elmer Fudd run over by a chipmunk. And yet this unremarkable specimen rose in the ranks of an established religion, broke off and created his own dangerous, fundamentalist interpretation of it, made it over with all manner of wondrous steampunk devices and automatons, infiltrated the upper caste of nobility in the City to the point where he installed all these gizmos in their prisons, businesses, and manor-homes, kept the Sheriff wrapped around his finger, kept extensive tabs on his enemies (Garrett, the Pagans), and was all set to go through with his mad holocaust of the flesh 'til Garrett turned the tables on him. Revenge of the Nerd indeed.
I remember that final level in his brass & iron cathedral with Karras piping in his demented ramblings through the ubiquitous sound system of the place. By turns angry, smug, exasperated, philosophical, solicitous towards Garrett, I thought was a good illustration of a man at the end of his tether. I remember one particular entreaty me made towards Garrett, asking him "What Hast Thou Built?" and feeling sorry for him because Garrett was a consumer, a parasite, not an architect and builder of things such as he. "Build thee a great HOUSE Garrett! That wouldst please the Builder mightily!!" A great antagonist to a game.
I contrast that to the baddie in the following Thief game (Deadly Shadows), Gamar or whatever the fuck her name was, who was one of the worst. A paint-by-numbers cliche in every way, she was such a tedious foozle her cutscenes were actually painful to sit through, I remember.
