Depraved Dwarf

Dwarfs (not those kind, the real kind) in fiction are fairly uncommon. When they do show up, they tend to be either comic relief or playing a fantasy creature. But then, there's these guys.

The Depraved Dwarf is a pint-sized bucket of malice. He (and it's pretty much always a he) is either a sadistic psychopath, a twisted rapist, or at the very least a violent, cold-blooded criminal. Can go hand in hand with The Napoleon, if the Depraved Dwarf's mysanthropy is implied to be a response - albeit blown out of proportion - to discrimination and abuse faced as a result of their short stature.

They tend to show up when the hero has been rendered helpless. Often, expect giggling.

Contrast Little People Are Surreal.

For villains with other disabilities, see Evil Albino and Evil Cripple.

Examples of Depraved Dwarf include:

Anime and Manga

Griffith from Berserk spends a whole year in the tender care of one.
"The Baby" from Monster, a neo-nazi and crime lord.
Mukotsu from Inuyasha is very small and toad-like compared to normal humans, and he's shown melting and suffocating people with his poisons. He also tries to do something nasty to a helpless Kagome, before being bifurcated by Sesshomaru.

Comic Books

Wonder Woman villain Dr. Psycho (pictured above).
Some incarnations of the Mad Hatter. Which is to say, both his height and level of insanity vary wildly. Gail Simone writes an especially creepy one.
- For that matter, some versions of the Penguin.
Gizmo of the Fearsome Five.
The Dummy combines this with Creepy Doll by pretending to be a ventriloquist dummy.
Fables revealed (or at least heavily implied) that the eponymous seven dwarves did bad bad things to Snow White during their time together, which is why she murdered them all.
Big Figure from Watchmen.
Le Bossu from Batman RIP.
Surprisingly averted in X-Men Noir, where Eugene Judd is one of the only good guys without any kind of pathology.

Fairy Tales

Older Than Feudalism: Rumpelstiltskin

Films -- Live-Action

Mini-me from Austin Powers is a lighter example. He's not that depraved, but he does try to eat a live cat at one point.
- Considering the stock he is cut from, the dwarfism is probably not the main cause.
Subverted in Foul Play; "The Dwarf" that Gloria is warned about isn't really a dwarf. This, of course, leads to confusion, and when she meets an actual dwarf, she goes nuts and throws him out of her apartment, seriously injuring him, only to find out he's really a bible salesman.
The title antagonist from the ''Leprechaun series of movies.
Death at a Funeral has the dwarf who blackmails the family with compromising pictures of him and the family patriach engaged in questionable acts.
Olaf, the title character of the Danish Exploitation Film The Sinful Dwarf, lures young women into an attic and locks them up. They are later used for prostitution. Yes, the word "depraved" might be a little light in this case.
Harry Earles plays what might be the Ur Example in The Unholy Three. He is easily the most vicious and evil of the titular trio, and pulls off the old 'midget in a baby carriage' trick.
Downplayed with Nick Nack of The Man with the Golden Gun. He's Affably Evil at all times, but he does work for a renowned contract killer, and does not hesitate to try and kill others when he feels like it.

Literature

In the book Obsidian Butterfly, part of the Anita Blake Vampire Hunter series, there is Nicky Bako, a pretty infamous necromancer who is the witch for the outlaw biker gang and werewolf pack in the area, Los Lobos.
This is what everyone thinks Tyrion is, despite his being one of the only characters that's basically good. But he may have had a Start of Darkness because of his ill treatment.
One gladiator in the second book of Detectives in Togas.
The Colorman from Christopher Moore's Sacre Bleu. Contrasted with Toulouse Lautrec who has a more or less heroic role.

Live Action TV

There's one in The Cape (trope), although he's more a Jerkass than outright evil.
Miguelito Loveless from The Wild Wild West is a cold-blooded criminal and Mad Scientist.

Music

Frank Zappa's "The Torture Never Stops" mentions "a sinister midget".

Professional Wrestling

Hornswaggle from the WWE universe.

Video Games

When Rubi gets captured in Wet, she's subjected to the attentions of a dwarf Torture Technician.
Salazar from Resident Evil 4.
As mentioned above in the Comics section, some incarnations of the Penguin are worse than others. The incarnation of the character from Batman: Arkham City however is probably one of THE nastiest interpretations of old Oswald Cobblepot in any form of media.

Web Comics

Dr. Knickerbockers from The Adventures of Dr. McNinja, who was actually based off of a recurring nightmare of the artists.

Web Original

Neo from RWBY is a female example. According to some definitions of dwarfism, an adult human dwarf is less than 4 ft 10 in. Neo is 4 ft 10 in in high heels -- and by any measure appears to be a sadistic psychopath.