Cue the villanous, over-the-top laughter. An evil voice is dripping with maleficence and mischief. There's no way you'd be thinking one of these voices belongs to one of the heroes, that's for sure. If your script calls for an ominous, bad-guy role, these voices should do the trick.
Some bad guys you love, and others you love to hate. Regardless, an evil voice is the hallmark of any self-respecting evildoer — where would the good guys be if there were no adversaries to defeat? Evil voices come in all shapes, forms, and sizes, and they can run the gamut from humorous and hyperbolic, to serious, grounded, and realistic. Sometimes you just need that perfect evil voice that will leave no doubt as to who is the one who commits atrocious acts and has the worst intentions.
There are as many possibilities for villains as you can think of. From evildoing alien races in a space opera, to warring dark mage factions in an RPG. Maleficence can take many forms. Some villains are practically archetypes, clad in dark clothes, without an ounce of goodness in their delivery; others are seductive, charming, but off-putting; others still are so over-the-top as to be hilarious. Whether your script is for fiction or for a commercial, nobody likes to see bad guys prosper.
Evil voices tend to sound relaxed, commanding, spacious. They tend to be on the lower end of the pitch scale, which gives them a slightly (or very!) intimidating factor. These voices usually revel in their own badness and villainy.