Villains who win against the hero and/or are successful in their ultimate goals (ie. Audrey II taking over the world with its children in the original ending of Little Shop of Horrors, Shadow the Hedgehog destroying, enslaving or saving the world based on the player's choices in Shadow the Hedgehog, and Thanos collecting the Infinity Stones to wipe out half of the universe's populace in Avengers: Infinity War).

They are, usually, the opposite of Incompetent villains (who do not succeed in anything), though some Incompetent villains CAN still be successful with a huge stroke of luck or with the help of much more competent evil-doers.

It should be noted that, for some, the goal wasn't to kill the main protagonist. Notably, Successful villains are very common in many modern-day horror movies (e.g. Freddy Krueger, Jason Voorhees, Godzilla, Kayako Saeki, etc.) as well as some tragic fictional works (e.g. Padre Damaso, Iago, etc) in which many of these villains succeeded in killing the protagonist in the end.

In many works, a Successful villain can be a Protagonist since protagonists are known for winning in the end.

Though these two categories often overlap, this is not to be confused with Karma Houdini, as these villains, despite their success, can still be defeated later, usually at the end of the story if their success occurred at the beginning or middle of it, or in a sequel since some villain victories open the doors for sequels (ie. Scar finally becoming the King of the Pride Lands after killing his brother and banishing his nephew, only to be dethroned by said nephew later in the movie, and Emperor Palpatine finally taking control of the Galaxy by manipulating the Chosen One, only for said Chosen One to betray and destroy him three sequels later).

Also, sometimes these villains finally succeed in their goals, but not the way they expected (Wile E. Coyote finally catching Road Runner, but only when he became too small to eat him, and Max Mordon obtaining immortality, but in the form of an undead mummy).