Villain Protagonist/Playing With

Basic Trope: The main character, viewpoint character and protagonist of a story is also the story's villain.

Straight: Bob Badguy is the protagonist of the story "Bob Takes Over The World", which contains Exactly What It Says on the Tin (of course). He acts in every way like a traditional Evil Overlord Big Bad, but is the main character who narrates the story.
Exaggerated: Bob is a complete Card-Carrying Villain who mercilessly and repeatedly breaks the fourth wall to lampshade how he's the villain of the story.
Justified: The story is Bob writing down his memoirs for posterity: Obviously he'll not be able to use anyone but himself as the viewpoint character.
Inverted: The Hero Antagonist.
Subverted: The story starts up with Bob Badguy for the first half of the book, before suddenly switching viewpoint and main-characterhood to Alice instead.
- Bob isn't really a Villain
Double Subverted: It eventually switches back to Bob for the final chapters, who remains the protagonist for the rest of the book. The parts narrated by Alice turn out to be unimportant in the grand scale of the story's narrative.
- Alice is example of Bait the Dog
- Bob is an Unreliable Narrator who really is a villain but has been trying to paint himself more sympathetically.
Parodied: Bob starts the story by beating up the narrator and taking his protagonist-hood by Hostile Show Takeover. The entire rest of the story concerns Bob abusing his narrator privileges to turn the narrative into a bad case of Her Codename Was Mary Sue, while the heroes try to break free from the story and boot him out of the narrator seat.
Deconstructed: Having Bob in charge does in no way lessen his villainy, causing the whole story to turn into a serious case of Black and Grey Morality where the distant and ineffectual heroes have no connection to the audience and the only people given care and attention are unsympathetic and evil. All the events that would normally be Offscreen Villainy in a traditional story gets described in livid detail, showcasing just how horrible villains are in such stories and how many lives get lost while the heroes tarry and go through their personal flaws and demons.
Reconstructed: When the heroes finally turn up, they turn out to be good and nice people, even as Bob's viewpoint tries (and fails) to paint them in an unflattering light. Bob eventually gets defeated in a traditional Black and White Morality tassle in the climax, with the final chapters being him lamenting his position from inside his Tailor-Made Prison and swearing eternal vengeance as goodness and light falls across the liberated land once more.
Zig Zagged: The story constantly switches viewpoint characters. Bob Badguy is only one of them, and is only the protagonist ever so often.
Averted: Bob the Blessed is The Hero. The story is a standard following of his hero's journey to take down Big Bad Alice McMalice.
Enforced: The writer wants to make a story where the main character is a bad guy and gets defeated at the end so we can see the rise and fall of a villain, who everyone knows are way cooler than heroes anyway.
Lampshaded: "Admire me?! You idiots! I'm the villain of this tale!"
Invoked: The land was taken over by the Forces of Goodness long ago; what with there being no more conflicts, the only way the story can have anything to do is if it follows up-and-coming wannabe Evil Overlord Bob on his path to upsetting the status quo.
Defied: Bob begins the story by ensuring us all that he is the hero, and this will not be one of those 'follow the villain stories'.
Discussed: Bob and Alice have a discussion over the traditional narrative roles of hero and villain, and note that so far Bob has been the one to go through the traditional hero's journey even though his goal is the malign one.
Conversed: Bob and Alice are watching a show where the villain is the main character, and have the above conversation.
Played For Laughs: Bob is an Unsympathetic Comedy Protagonist or a Heroic Comedic Sociopath with a 'villanous' goal, Laughably Evil, or a Harmless Villain whose 'evil plan' is villainous but completely harmless.
Played For Drama: Bob is a true Evil Overlord, and does some truly horrifying things. The story treats him with every bit of reverence as deserved and does not sugarcoat any of his horrible deeds.

Now follow this link back to Villain Protagonist if it pleases you, your vile troperness.