I ran a paragon half blue dragon balor named Desacretu against my PCs since level 3, and he was the mastermind and the enemy until nearly level 50. They thought they had killed him several times, but even after receiving deific onslaughts he survived. Later they find out he wouldn’t kill them because one of the PCs (a half red-dragon human orphan, his egg was frozen for millenia) was the son of one of his old comrades (a Paladin, whose mount was a Lawful Good red dragon, the PCs father, who later united all dragons for a few millenia, but that is another story).

In another campaign, using the Major Artifact “Shield of Prator” in the DMG as an idea launcher, they have characters playing 7000 years before their former characters in Prator’s campaign to Hell, and Desacretu, completely sane, is their field commander. He follows Prator blindly, but when Prator is slain by Bel, Mammon, and Dispater, he despairs and is driven insane.

One of the characters in that crusade had the Saint template, and was thus immortal and did not die when affected by an imperfect temporal stasis spell, and I allowed his PC to run him again, 9000 years after the crusade. Eventually Desacretu was defeated because he could not strike down someone who so perfectly mirrored Prator; his hope was restored and he died.

That was a bit longer than I intended, sorry.

Another alternate recurring villain idea would be to have a former PC (perhaps all members of his party died, and a new group was decided upon jointly by the players) as an enemy, or an old, too powerful cohort, or maybe the entire campaign is centered around destroying a Church of Hextor or a Drow city.

You don’t need the cliche recurring villain to gain the same feeling of repeated and angrifying thwartation (two new words, I hope you understand their meaning).

Now when the Heroes kill off the charismatic villian, the twin will want to take revenge. This can be done in several subtle and enjoyable ways such as sending “haunting notes” to the players or making brief appearances for the players to spot. This can lead to the players believing they’re being haunted by the slain villian. :)

The players (if they’re the sort that like to think) can have fun finding out that the slain villian had a twin and now the search is on to find the missing half that has been hounding the players!