Your Applied Phlebotinum doomsday device has been activated. The MacGuffin is within your grasp. The good guys are locked away in the Death Trap. Your circuitous Evil Plan is three-quarters complete! You know what, screw being the Evil Overlord of the world — you're already a god! There is only one thing left for you to do — but first things first:
Muahahahahaha... Hahahahahahaha... AAAAHAHAHAHAHAHA!
The Evil Laugh. Don't knock it 'til you tried it, folks.
This became an Undead Horse Trope long ago and usually will produce nothing but pure Narm. There are only a few characters who are able to get away with this in modern media:
A famous supervillain who's been doing this since before it was cool,
A villain inspired by the classic ones. Will often do this while twirling their mustache or doing the old Flourish Cape in Front of Face.
A very old wizard-type fellow or Mad Scientist for whom this just comes naturally,
A bona fide psycho, in which case you'd better do some pretty impressive cackling,
A Card-Carrying Villain who does it because it's a classic villain maneuver,
For a Wicked Witch this is something she may do, a good, hysterical cackle is practically the leitmotif of any evil witch worth her brew. Ee-He-He-He.
A Monster Clown. Would The Joker be as scary as he is today if he were only a mime?
And those who succeeded their plans will also do this, because they're in delighted mood.
Anti-heroes or certain types of Guile Hero may also do this if they out gambit the villain; they may do it because they are unconcerned with what society thinks of them or because it is such a well-known classic villainous maneuver.
In any case, it has since devolved to the occasional evil chuckle (which may or may not be a bit scarier) or so every once in a while, except in certain cases, and the trope of laughing while your victim is helpless is definitely dead, as modern villains usually laugh while they work (to much better effect). A common subversion is to have a villain have an Un Evil Laugh, with snorting, chuckling, and squeaking, especially if they are a villain in a comedy series. Similarly, a common parody is to have the laughing villain start coughing or sputtering if they laugh long enough or hard enough. On the other hand, a Giggling Villain can be menacing without doing a proper laugh.
Just remember, you Genre Savvy villains, the Evil Overlord List:
20. Despite its proven stress-relieving effect, I will not indulge in maniacal laughter. When so occupied, it's too easy to miss unexpected developments that a more attentive individual could adjust to accordingly.
Truth in Television: Passionate laughter, like screaming, is a great relief for stress and adrenaline, with the added benefit of embarrassing and taunting self-conscious opponents. Just don't take it too far in public.
Compare Noblewoman's Laugh, Evil Is Hammy, Evil Gloating, Evil Has a Bad Sense of Humor, Drunk on the Dark Side, Giggling Villain, Laughing Mad, and Laugh with Me! When it looks like the villain is defeated, but then they pull this out, it's Ominous Adversarial Amusement. It's even more jarring (and awesome) when the villain in question is an emotionless character.
Here is a compilation with a lot of examples of this trope.
