Never Be Hurt Again

This is a fairly common stock motivation, in which a character who has been abused, persecuted, or otherwise mistreated in the past is acting to make sure that this sort of thing never happens to them again. This can encompass anything from taking a few levels in badass to ensure they'd be able to defend themselves against future threats, to attempting to Take Over the World and overthrow the oppressive institutions that made them miserable. The character may also wish to spare others from suffering like they did, but there needs to be at least some element of preemptive self-protection involved to fit the trope.

It's a common motivation for the behavior of the Broken Bird. See also Freudian Excuse and My Greatest Failure. If the hurt is romantic in nature and new relationships are avoided for this reason, it's The First Cut Is the Deepest. See also Hope Is Scary, where recovering from despair is feared because it doesn't allow this.

Examples of Never Be Hurt Again include:

Anime and Manga

The backstory for Crest of the Stars has the Abh overthrowing their human creators and masters, then going on to conquer most of the known universe, while in the process of conquering the rest.
In all adaptations of Astro Boy, Dr. Tenma's son is killed. In grief, Tenma builds a robotic replica of his son, Astro Boy, and because he has plenty of Mad Scientist in him, augments the android with ridiculous amounts of weaponry so that his new son can defend himself when threatened. In a more direct version of this trope, Astro constantly sees robots getting mistreated or destroyed, often himself included, and spends much of his time defending robots without harming humans.
This is the reason Minatsuki acts the way she does in Deadman Wonderland. To keep anyone from abandoning her the way her mother did, she deliberately acts as crass and cruel as she can so that no one will ever get close to her.
The manga tie in for Devil May Cry 3 suggests that this is Dante's main motivation. After losing his mother to demons, he didn't get stronger to protect other people, it was so nothing like that could happen to him again.

Comic Books

Magneto, when he's given sympathetic motivations. He's a Holocaust survivor who doesn't want mutants to face the kind of genocidal bigotry he endured in his youth.
Some portrayals of Poison Ivy in Batman - she got mutated when she fell for a guy Playing with Syringes - now she is obsessed with controlling men.
In the "Siege at Blue Mountain" arc of Elf Quest this seems to be Winnowill's motivation for wanting to take all of the pure-blooded elves somewhere they can never be hurt again. For many of them it doesn't end well.

Film

Scarlett O'Hara in Gone with the Wind: "As God is my witness, I'll never be hungry again!"
This has been used as Spartacus' motivation in several adaptations.
In Ip Man, Jin says that he vowed to never go hungry or suffer again as a Shut Up, Kirk when Ip tells him at the factory that no one forced him into a life of crime.

Literature

The main character of The Kingkiller Chronicle mentions this as one of several motivations for attending Wizarding School. (How truthful he was being is currently unknown—especially since the series isn't finished yet.)
Alan Dean Foster's The Man Who Used The Universe. Kees vaan Loo-Macklin creates a criminal empire and a legitimate business empire and manipulates too many beings to name (both human and alien). He does this because he was abandoned as a child and grew up in a series of foster homes where he was mistreated because of his appearance, and was determined never to be helpless and mistreated again.

Live-Action TV

House in House seems to be like this at times. His relationship with Stacy sent him into one period of emotional disengagement. Then when after his relationship with Cuddy goes bad, he refuses the affections of his green-card wife, apparently out of fear that sex with anyone who actually likes him (rather than hookers) might lead to attachment which will hurt him again. Of course, if you showed him this page on TV Tropes and said that it applied to him, he'd probably give you a Hannibal Lecture about what a moron you are for thinking it.
Doctor Who:
- John Lumic, who has some undisclosed and presumably painful terminal illness, decides to enforce Unwilling Roboticisation upon himself and humanity in order to eradicate death and emotion.
- Professor Lazarus from "The Lazarus Experiment" tried to create a device to avoid death due to his experiences during World War II. It didn't quite work out.

Music

The Simon and Garfunkel song "I Am A Rock" seems to describe the feelings of someone who doesn't want to love anymore because they were hurt by it once.

Tabletop Games

Warhammer 40,000 and Warhammer Fantasy Battle: several justifications for falling to Chaos are protection against that god's particular domain. Mostly seen with Nurgle, the god of disease, whose followers are infested with pus-filled growths and oozing sores, but are no longer negatively affected by them, instead reveling in every new pox they develop.

Video Games

Squall Leonhart of Final Fantasy VIII. The reason for his cold, detached demeanor was because his fellow orphan and sister, Ellone, left him alone as a child and he developed abandonment issues. He feels that, eventually, all friends and family die or go away, and the only way to avoid the pain from that is to never let anyone in again.
The main antagonists in Star Control II, the Ur-Quan, have this motivation: they were once enslaved and hideously mistreated by the Dnyarri, and after winning back their freedom while suffering constant excruciating pain (which protected them from Mind Control), they decided the only way to make sure it never happened again was to enslave (Kzer-Za) or exterminate (Kohr-Ah) everybody else first.
This is Drakath's motivation to become the Champion of Chaos in Adventure Quest Worlds, according to the end of the They Might Be Giants event, which saw him being kidnapped (along with the Hero and the TMBG members) by a crazy alien collector.
In League of Legends, after Professor Stanwick Pididly stole credit for both the creation of Blitzcrank and the technology that revived Urgot, Viktor decided to protect himself from this happening again with his newest accomplishment - the transformation of himself into a killer cyborg. This both removes (mostly) the pain and anger he feels over his inventions being stolen, and demonstrates his own skill in a way that can't be stolen.

Real Life

Many nations with a recent or ancient history of being oppressed have carried this sentiment into the modern day, which results in rather thorny foreign policy. The problem is particularly severe in Africa and the Middle East where this trope often leads to violence but many other countries with reputations for being 'hard' or 'rugged' have felt this influence at some point.
Common with former slaves.
- The Haitian revolution was originally put down under Napoleon, but after the French let their intent to re-enslave the Haitians be known, the war reignited and eventually led to the end of French Rule.
- Nat Turner's Rebellion, which involved killing all of the whites the rebels came across, was started for similar reasons.
It's been argued that sociopathy is really just an adaptation to help one survive in extreme situations. Which actually makes sense looking at some of the traits; incredibly diminished empathy, desire for control, doesn't trust others, etc.