Battleaxe Nurse

If Mr. McMurphy doesn't want to take his medication orally, I'm sure we can arrange that he can have it some other way. But I don't think that he would like it.

—Nurse Ratched, One Flew Over the Cuckoo's Nest

Nurses, like doctors, are usually good in fiction. After all, a person who works to save lives can't possibly be evil, right?

Not in the case of the Battleaxe Nurse.

The Battleaxe Nurse is an incredibly sadistic and cruel nurse, often older (and uglier) than her more angelic counterpart, and Always Female. She gets her kicks from kicking patients, the weaker the better. If she isn't already the head nurse, her cruelty gives her a degree of power over both the patients and the other nurses. Anybody who goes against her ends up injured or worse, and she jumps at the chance to give a particularly rebellious patient a lobotomy. Sometimes the Battleaxe Nurse has a hint of the Mad Doctor in her, especially if she decides to test interesting new drugs on her helpless patients.

The most famous example of this trope, if not the Trope Maker, is Nurse Ratched from One Flew Over the Cuckoo's Nest.

There's also a milder version more common in comedy. This version is still hugely unsympathetic and enjoys having power over the patients and other nurses, but can still say with some justification that everything she's doing is for the patients' own good (although the patients are unlikely to see it like that). In British works, she almost certainly has the title Matron and is played by Hattie Jacques (who actually was a Red Cross nurse during W.W.II).

A subtrope is the Triage Tyrant.

Examples of Battleaxe Nurse include:

Anime and Manga

Katherine from Gregory Horror Show. A rather perverted pink lizard nurse with a needle the size of herself which she.....seems to REALLY love draining all the blood out of people with.
Mako Yakumaru from Rosario + Vampire has an injection fetish. Her injections temporarily turn people into her slaves, and proceed to help her carry out homicidal Antithesis missions.
Played straight and including a souped-up Mad Doctor version in an episode of the Sorcerer Hunters anime. A hospital run by two women who use the facility as a cover for torturing male patients because they've been betrayed by men in the past.
Prison doctor Rei Takashima of the titular Deadman Wonderland, though calling her "doctor" is putting it nicely. She gets sadistic pleasure removing the body parts of fully conscious Deadmen when they lose a Gladiator Game. She happily skips into the Moral Event Horizon when gleefully removing the right eyeball of Badass former cop, Senji Kiyosama after losing to Troubled but Cute protagonist, Ganta. She makes a full jump into Complete Monster territory when last seen creating a hideous abomination of combined forgeries (fake Deadmen who were former prisoners brainwashed into becoming drugged up killing machines) before being unceremoniously killed by the Ax Crazy Wretched Egg.

Comic Books

Nurse Lois from Frank Miller's Daredevil: Born Again story arc is a gruff, intimidating nurse who supervises Nick Manolis' recovery. She's also a mob enforcer for the Kingpin who breaks Ben Urich's fingers and kills Manolis.
During Jason Aaron's run in Ghost Rider, Ghost Rider fights an army of these at some point.
Fables has Mrs. Sprat. It turns out she became a nurse out of immense jealousy towards all the other beautiful Fables, for the chance to have them on their backs and completely at her mercy.

Film

As mentioned above, Nurse Ratched in One Flew Over the Cuckoo's Nest.
The uber-example of a comic version would be Hattie Jacques' character in the various Carry On films.
The interrogation scene in The English Patient probably qualifies.
The Right Stuff has a Battleaxe Nurse conducting tests on the potential astronauts.
The Mel Brooks film High Anxiety has Cloris Leachman as the rather grotesque Nurse Diesel.
Foxy Brown's boyfriend has a nurse who doesn't take kindly to his state of arousal after Foxy's visit.

Literature

As mentioned above, Nurse Ratched in One Flew Over the Cuckoo's Nest.
Annie Wilkes in Misery, who has the bonus of being a Yandere Loony Fan.
In "Down on the Farm", a short story by Charles Stross, the Laundry's Bedlam House is run by a deranged, demonic 1960s mainframe called "Matron", and three robot "Sisters" slaved to it. As in Futurama, one of the nurses is called Nurse Ratchet.
The senior nurse in Going Postal, who seems to be a little hazy on the difference between a hospital and a prison. Dr Lawn, supposedly in charge of the hospital, claims that the only way to deal with the nursing staff is to throw a handful of chocolates in one direction and then run in the other as fast as possible.
Assignment Gestapo by Sven Hassel. Tiny falls in love with the (so-called) milder version, because she's the first woman he's met who's tough enough not to take any abuse from him.

Live-Action TV

Supernatural had one of these as the Ghost of the Week in "Folsom Prison Blues".
Dexter's first victim was a mad nurse who slowly euthanized patients—willing or not.
In the 4th season of Farscape, the We're So Screwed 3-parter had one of these torturing/testing Aeryn and her unborn child.
- While she is never referred to as a nurse, Tauza is presumably one of these. She is the only person to ever interact with Scorpius while he is a child and is said to be the one who treated him for heat delirium. She also enjoys tormenting him, including one occasion where she turns up the heat in the room (which he can't stand due to his hybrid physiology) and forces him to crawl to her to get water. When he says "please", she dumps it on the floor and hits him.
Mrs. Raven from the British sitcom My Hero (TV). Fond of such things as staging a fire drill just to torment geriatrics, hypnotizing patients into giving her their money, and blackmailing her boss to secure her position. At one point, upon gaining superpower, she goes on to become a multinational supervillain for an episode.
- She's also an administrator, not a nurse. God forbid her job should involve helping people.
Averted, oddly enough, with Major Margaret "Hot Lips" Houlihan of Mash. While she was generally depicted, especially in the early seasons, as a humorless and short-tempered authoritarian in her interactions with the rest of the staff, her manner with the actual patients was always kind and caring.

Web Comics

Jeremy's stalker in Platinum Grit becomes this for a while.
One appeared in Shadowgirls. Unfortunately for her, Mrs. Snow was currently friendly to her victim, around, more skilled at trampling people into dirt and "needed the exercise".

Western Animation

Futurama has the robotic Nurse Ratchet, an obvious parody of Nurse Ratched.
The Flintstones had one of these show up when Pebbles was born. A few other times, too.

Real Life

A 2006 Guardian article reports that a male nurse in an English hospital poisoned a bunch of patients just so he could impress people when he resuscitated them. Problem was, in two cases the resuscitation didn't work.
There was also a story in the Toronto Star once about a young American nurse who fatally poisoned three patients (and never attempted to revive them) to impress her friends.
There were four Austrian Nurses dubbed the Lainz Angels of Death who killed 49 elderly people by flooding their lungs with water.
During the World Wars there were several horror stories going on in the front about sadistic nurses who enjoyed tormenting the wounded soldiers, some which apparently were true.