For a slightly different take on this, I'm going to nominate a villain that is known to literally dozens of people, all of whom have played in my home campaign.
Yes, I nominate all those named NPCs, made for home campaigns (or in my case kind of inherited and then
borrowed for my home campaign). The nameless, or named, lived for one session or multiple campaigns. Bringers or darkness and terror one and all.
For my token villain I nominate my longest running villain Lady Svargiv, the black wizard. After unsuccessfully trying to sacrifice her own son at his coming of age ceremony to power her immortality she made a pact with dark powers and became an all-powerful lich bent on destruction of all mankind. Villain of several home campaigns, often behind the scenes.