Due to Values Dissonance, some stories in The Bible will seem like this to modern readers. The Atheist Experience, for example, has called the very concept of Hell "an infinite punishment for a finite crime," making it inherently disproportionate no matter how heinous your sins are.
After Cain murders his brother Abel, God makes the strange decision to protect Cain from retribution through the threat of retribution. "Then the LORD said to him, 'Not so! If anyone kills Cain, vengeance shall be taken on him sevenfold.' And the LORD put a mark on Cain, lest any who found him should attack him." (Genesis 4:15). Cain himself had done such, by murdering his brother for beating him in a contest.
A few verses later, Cain's descendant Lamech makes this arrogant claim: "I have killed a man for wounding me, a young man for striking me. If Cain’s revenge is sevenfold, then Lamech’s is seventy-sevenfold." (Genesis 4:23-24)
Like several vengeful passages from the Torah, this one is turned on its head by Jesus. "Then Peter came up and said to him, 'Lord, how often will my brother sin against me, and I forgive him? As many as seven times?' Jesus said to him, 'I do not say to you seven times, but seventy times seven.'"
In the book of Judges in the Bible, the Philistines bind Samson, gouge out his eyes, and make him entertain them. (This was after he had already killed thirty Philistines in order to steal their clothes, "struck down" 1,000 Philistines who were sent to capture him, and killed members of the Philistines who were ruling over his people on other occasions.) He asks for strength, saying, "let me with one blow get revenge on the Philistines for my two eyes." He then performs a suicide attack in which he pushes apart the pillars holding up a building with 3,000 men and women on the roof, "So the dead whom he killed at his death were more than those whom he had killed during his life."
In 2 Kings, the prophet Elisha is mocked for being bald by some local youths. Rude, sure, but God summoning two she-bears to kill (or at the very least maim) 42 of said youths might have been overreacting just a tad...
The "youths" at the time were likely teenagers ("laboring in the fields") and the "stones" they threw were more akin to bricks. So it was less little kids calling him names and more a gang of young toughs telling him "You don't belong here, Jew-boy."
Then there's Haman, resident Evil Chancellor to the king of Persia. Mordecai refuses to bow to him. Haman attempts to perform genocide on the Jews for this insult.
A man gathers wood on the sabbath. This counts as work, so he's stoned to death.
A lot of the "sins" in the Bible, which can all be punished pretty harshly, fall under this trope. You can stone a child to death for being disobedient, or be punished for wearing mixed fabrics or planting two crops in the same field.
Granted, said punishments are only shown in a decent light in the Old Testament. In the New Testament, Paul says that these old Jewish laws are no longer required, since Christ died to save us from that (such as his reprimanding of the Galatians in Galatians 3).
And even Jews today recognize those laws are somewhat outré. The Talmud has made the application of those laws almost impossible to put into practise (i.e. requiring four witnesses, requiring the offendant to express his intention, etc.), as the Rabbis knew that Draconian justice did more harm than good for the general adherence to the law. In such situations, the secular law eclipses the religious law.
Even Christ Jesus himself dabbled in this once when he cursed a fig tree to wither and die for the horrible crime of not bearing fruits when he was hungry, simply because it was off-season. Of course, even that served as a lesson in how faith can make the impossible possible.
Granted the tree, being a tree, probably didn't really care.
Greek Mythologyloves this trope. The below examples are proof that if you piss off the Greek gods in a dream, you had better wake up and apologize.
Prometheus stole fire from the gods to give to man. This allows mankind to create civilization, which Zeus didn't want, so he's chained to a rock for eternity. Every day, buzzards peck out his liver, which regrows every night.
It's a little bit more complicated than that. Zeus orders that humans make sacrifices to the Gods, but demands that they give up all the usable parts. Prometheus, upset that his creations are getting treated this way, comes up with a plan: he has the humans slaughter a cow and divide it into two bags; one contains all the meat with a layer of gristle on top, while the other contains the offal with a layer of fat on top. Zeus naturally picks the better-looking bag, meaning humans get the meat and the Gods get the garbage parts. Angrily, Zeus declares "Man shall have his steak, but he shall eat it raw!" and takes fire away from them. Prometheus sneaks into Mount Olympus and steals the fire back, which is why he got the aforementioned punishment. The disproportionate retribution comes from Zeus' ensuing punishment of humanity, which gets forgotten in most tellings.
Witness Apollo, who was challenged to a contest of music by a satyr named Marsyas. When it was determined by the Muses who were overseeing the competition that both were equal, Apollo, in a total dick move, decreed they play and sing at the same time. As Apollo played the lyre, this was easy to do. Marsyas could not do this as he only knew how to use the flute and could not sing at the same time. Naturally, Apollo was declared the winner. He proceeded to flay Marsyas alivefor his hubris to challenge a god.
Apollo also played a role in the fame of Cassandra. Apollo gifted her with the ability to see the future, but when he tried to seduce her, she refused him, so he cursed her so that her prophecies would never be believed.
A woman named Arachne who fancied herself a better weaver than the goddess Athena. Athena challenged her to a competition, and it turns out Arachne was indeed the better one. This pissed off Athena sufficiently that she turned Arachne into a spider, so that she would spend the rest of her days doing nothing but weave. In other versions of the story, Athena bests Arachne using her divine powers, and turns Arachne into a spider only after Arachne kills herself in despair.
Some versions of this claim that in the contest, Arachne weaved a tapestry mocking the various foolish acts and infidelities of the gods. So whether it was losing, being mocked, or being shown up AND mocked, Athena was pretty angry about the entire thing and tore down the tapestry, causing Arachne to kill herself. Afterwards, Athena turned her dead body into a spider, though whether for punishment or out of some remorse, the story varies.
Another version says that Athena was upset but not PISSED OFF, and actually wanted to warn Arachne that she was too proud for her own good. (Pride being one of the worst sins that humans could commit against the gods). So she disguised herself as an old woman and tried to have a pep-talk with Arachne herself, but she spurned Athena's warnings and boasted again about her skills. Only THEN Athena got pissed enough to enact the trope.
Probably the most hard-done of all was Medusa and her two sisters Euryale and Stheno, the gorgons. Some versions of her story have them being turned from beautiful maidens into hideous monsters by an angry Athena because Medusa, a priestess in Athena's temple, had sex with Poseidon. Disproportionate? It gets worse in other tellings, in which Poseidon actually RAPED Medusa.
Niobe (half-goddess) thought it unfair that the goddess Leto was honoured more than her because, among other things, Leto had only one son and one daughter, Niobe has seven of each. In an extra-dickish move, even by Greek God standards, Leto has her son Apollo kill all her completely innocent sons and her daughter Artemis kill all her completely innocent daughters (except one in some versions of the story). For extra cruelty, the daughters are killed right in front of their mother. The real reason Niobe should be honoured more than Leto is that Niobe was not a complete dick.
Tiresias gets a variety of these, depending on the story. In one story, he's punished for hitting two copulating snakes with his stick by getting turned into a woman. He's later blinded when he contradicts Hera by saying that women enjoy sex ten times as much as men. In another version, Athena blinds him when he accidentally sees her bathing, and his legendary powers of foresight were her way of apologizing since she couldn't undo the effects.
Actaeon accidentally glimpses Artemis naked, so she turns him into a stag and has his own hunting dogs rip him to pieces.
The Trojan War was (ostensibly) started because Helen of Troy ran off with Paris. The Greeks commence a ten-year siege of Troy, and eventually sack the city, enslave all the women, and kill off the men. Values Dissonance factors in here, because the Greeks took the law of hospitality very seriously. Also, many of Helen's former suitors swore to do just this if she should be kidnapped.
Even worse. The entire mess began when Paris was asked by Aphrodite, Athenea and Hera to judge which of them was the fairiest (after Eris, Goddess of Discord, threw a golden apple saying "To the fairiest"). Paris was undecided, so the three tried to bribe him: Athenea offered wisdom, skill in battle and great ability to fight; Hera, dominion over all of Asia, and Aphrodite the love of the most beautiful woman in the world. Paris picked Aphrodite, earning himself the enmity of the other two goddesses.
After Achilles kills Hector for having killed his cousin and "best friend" Patroclus, he strings up the corpse and rides it around the city a number of times, then refuses to give it up for a proper burial. This was seen as being somewhat beyond the pale, and Achilles should have laid his retribution to rest once he'd killed Hector. It takes King Priam's stirring pleas to get Achilles to relent enough to let the grieveing father buy the dead body back in exchange for a huge ransom.
Aphrodite, goddess of love, cursed Theseus' second wife, Phaedra, to fall in love with Theseus' son by his first wife, Hippolytus. After he rejected her, she committed suicide and claimed in her note that Hippolytus had raped her. Theseus laid his own curse on Hippyoltus, who refused to tell the truth in honoring an oath not to reveal that Phaedra had come on to him, resulting in Poseidon killing Hippolytus. Why did Aphrodite cause this to happen? Because Hippolytus chose to worship Artemis instead of her.
While trying to prevent the birth of Heracles, Hera was deceive by Alcmene's servant Galanthis into thinking Heracles had already been born. Hera subsequently turned Galanthis into a weasel for tricking her.
Not to be outdone, Gaia instigated a fair number of the divine conflicts, usually as escalation from a previous conflict. In revenge for his overthrow of her children, the Titans, Gaia gave birth to the Giants by Uranus and Typhon by Tartarus and turned them lose on Zeus, never mind that Cronus was guilty of the exact same crimes he had killed his own father for.
Loki's eldest son, Fenris, was chained to a big ass rock until Ragnarok because the gods foresaw that they would experience "great troubles" from his rapid growth. That's right. He was imprisoned until the end of the world for something he hadn't even done yet. He gets his revenge by killing Odin at Ragnarok.
Another of Loki's sons, Narfi, was killed for Loki's crimes, meaning he hadn't done anything to deserve it. Odin turned his brother Vali into a wolf that killed him and then used his entrails to chain Loki to a rock until Ragnarok.
Loki tricked Baldr's blind brother Hodr into shooting Baldr with (variously) an arrow or spear, which killed Baldr. In response to this Odin lay with the giantess Rindr, who gave birth to Vali, who grew up in a single day and killed Hodr, even though Hodr was barely responsible for Baldr's death. Loki meanwhile walked away scott free, only receiving punishment for it and a number of other crimes much much later.
Lara, one of the minor Goddesses of Death in the Roman Pantheon, used to be a quite cheery and lively nymph. That, until, according to the different versions of the myth, she either warned her sister Juturna and the goddess Juno about Jupiter's plan to rape her, or told Juno about a long-standing affair between her husband Jupiter and Juturna. In both versions, Jupiter saw fit banishing her to Hell, but just for added safety had her tongue cut out first. Just because that wasn't enough, Jupiter had Lara escorted to Hell by her son Mercury, and when Lara tried to bargain for at least her freedom, Mercury just raped her on the spot, thus giving birth to the minor gods of streets.
In Slavic Mythology, Veles, god of water, magic, earth, and the underworld, had a habit of stealing things from Perun, the god of thunder, fire, and mountains. Every time this happened, Perun's response was to chase Veles and blast the bejeezus out of him with lightning. And anything that Veles attempted to hide behind also got zapped, up to and including houses and people. Granted, the stuff Veles stole from Perun included his cattle (very important back in the pre-Christian days), his wife, and his son, but still, zapping innocents who just happened to be used as hiding spots is kinda overdoing it...
The Koans in Zen Buddhism are mental exercises to learn thinking out of the box and overcoming the limitations of conventional thinking. Some are just a short sentence, while others are short stories which very often feature highly disproportionate acts of violence to make the absurdity of the situation more obvious and remind the pupils not to think of it as an actual event.
And The Fair Folk were prone to brutally avenging slights so minor that their victims were often completely unaware that they had done anything wrong in the first place. In fact, this trope is the reason they're called The Fair Folk — because anyone who even suggests that someone fairer than they even exists will bring on their wrath.
In several religions that believe in Karma, it's said that any negative karma will come back to the offender only 7 or more times worse.
The Sphinx cursed Thebes with a deadly plague that lasted several years. Why? He had told the Thebans a riddle and then gotten offended when they couldn't solve it.