For video games, it's a tie between Ganondorf from Legend of Zelda, Dracula from Castlevania, and Ultimecia from Final Fantasy VIII. Three of the finest, most charismatic examples of the Dark Lord archetype, more complex than most and with a few redeeming points.
From movies Darth Vader the legend Star Wars is about, and Queen Bavmorda from Willow, for being scary as hell and a rare female Dark Lord.
Let's face it, in far, far too many cases here, people idea of an article is to overbloat the infobox, gallery, quotes, and categories, leaving zilch in the actual friggin' page. It's like stating that a skeleton is enough for a body to work, which is not.
Look at the neverending category abuse that plagued us ever since the beginning, look at the gallery pages filled with countless pictures of the same moment, look at the quotes segments listing the villains' entire dialogue.
The very last thing we need is yet another mean to make users focus on what's meant to articulate the article instead of write the article in the first place.
Against.
It's unnecessary, villains have no friends or very rarely and are ennemies to the entire cast.
Infoboxes are already loaded