Seems a little cliche, but cliche is cliche for a reason.
Biggest advice is find non standard motivations, slash occurances for the Villain to assume.
Rather than make him a Lich, and her a Vampiress have it turned about and have it be his fault that she is...whatever she is...possessed by a legion of demons (that gives her little in the way of strength, but has been making her do things that she wouldn't normly do).
Perhaps she was felled in a combat and in a failed attempt to revive her our wizard friend bungled it and brought something else along for the ride, (an incoporeal undead of some sort could work as well). In his process to find a cure for her he himself slowly comes under the effect of the beast inside, then when his companions come to put an end to her after some brutally horible deed, murder, serial murder, wiping out a whole village, poisoning a well, etc.
In his vulnerable state the wizard kills his friends, and closest allies only to have them also be raised as this form of beast.
After a brief encounter with the new party...this wizard...half mad from grief, and poised on the brink of total insanity grabs hold of a master plan to send the party down into the bowels of hell or worse to vanquish the creature that even now whispers at him, trying to control him.
Of course the party is destined to succeed, and like you have said, in the process something aweful occurs and the possessed love, along with the now revenenant companions cease to live, and worse are sent to spend eternities in the pits of hell itself (or some other equivelent horrible place) in brutal torment for the rest of their immortal lives.
This sends the already broken wizard over the edge, and though it was his scheme that brought about this fateful end, he points his finger at the party, "It's you, you vile demons in disguise" "your fault, your fault" and unleashes his fury upon them (of course it happens just as they return from the adventure, happy and victorious, unsuspecting people that they are).
Bruised and beaten the party retreats, no sign of their client turned nemesis, though whether he returns as half fiend, lich, greater wraith, or otherwise he now hounds, and haunts the parties every step, a creature possessed by a fiery hate, and with an insane apetite for revenge.
As an aside I would make them someone the PC's know and trust, someone they actually think of as a kindly man who would never hurt anyone. Once he kills the former companions however he is on a vicious downward spiral that the players might not ever suspect, though little things like forgetfulness, calling one of the female characters by his lost loves name, or chatting with the air as if it were one of his former allies might help to give a sense of unease.
I personally would stay away from lich, its over used, and not as scary as some other things could be. You could use him as a pawn for a fallen god who is coming back from the dead, through his bungled attempt at a resurrection.
