In Oblivion, merely being the Hero of Kvatch, Archmage of the Mage's Guild, Guildmaster of the Fighter's Guild, Champion of the Arena, the Divine Crusader, Champion of Cyrodiil and, (in the expansion) Sheogorath's heir, the new God of Madness, isn't enough to make highway robbers leave you alone. It could be a bit of a subversion: thanks to the feature that makes the enemies level up with you, bandits can still be quite tough for a while (although most NPCs have their levels capped, so at higher levels this trope is still in effect). Though the robbers get downright silly at high levels. They always ask for 100 gold, no matter when it is that you face them. At low levels, this can be a burden to pay. At higher levels, 100 gold is practically spare change. Plus, since the robber's equipment levels with you, the people demanding one hundred gold are wearing glass armor that's worth thousands. However this is truly averted if you are the grey fox and wearing the Nocturnal's Cowl. Then the highwaymen turn into fanboys and won't attack you unless you attack them first. There's actually a little known trick to escaping them. If you're wearing less than 100 gold worth of equipment when they speak to you (not carrying, just wearing), you can claim you don't have the money on you. They fall for it even if you're carrying 499lbs of daedric equipment in your pack.
Alternatively, if you do plenty of fame-increasing quests (the main quest in particular), the highwayman will instead greet you normally.
In Skyrim, you can actually respond to a random highwayman ambush by telling the moronic robber that "I don't have time for this" and walk away. Or intimidating them into letting you go. Or, if you've completed the Thieves guild questline, pointing out that you're their boss, before proceeding to shake them down for cash instead!
Skyrim even has a specific isolated example in Ravenscar Hollow, a cave occupied by a pair of hagravens and their minions, including a cave troll. Partway into the cave, the player can find a caged bandit who begs to be released and will help you out; after you defeat the monsters (again, the very same ones that captured him and all his buddies), he announces his intent to rob you blind.
Random brigands attack all through Baldur's Gate I and II, despite the fact that you're equipped with glowing weaponry, armor made from dragonscales, and frequently outnumber them. They finally get wise in the Throne of Bhaal expansion, when the closest thing to random bandit encounters is when a group of vampires lure you in, then realize who you really are, and their leader gives a Rousing Speech that includes something about her and her allies being mercilessly slaughtered. Also, while in Saradush you can make thugs and ruffians piss their pants by announcing that you are a Bhaalspawn. In Baldur's Gate II, you will occasionally encounter thugs while moving around in the city, who will try to kill and mug you. If you are strong and well-known enough, the thugs will have half the brain to say "It's CHARNAME, run for your lives!!!"
Grand Theft Auto IV has serial killer Eddie Low have much hype about being a terror in Liberty City (he's killed a dozen people, most either unsuspecting joggers or hitchhikers). The optional encounters with him ends with his trying to kill Niko, who fought in the Balkans and is now a freelance "problem solver" (read: he's killed a few hundred people, at least, most of which include armed thugs and police). It's pretty obvious how this one turns out.
In Grand Theft Auto V, shifty car dealer Simeon Yetarian sells a yellow SUV to an unsuspecting victim, waits for the payments to fall through (as planned), and then sends his repo man Franklin Clinton out to take it back. The plan almost works out, except for a certain hitch: the victim in question is James "Jimmy" De Santa, the son of former bank robber and Retired Badass Michael De Santa, who immediately catches on to the scheme. Hiding out in the back of the SUV, Michael allows Franklin to repo it, then puts a gun to his head and forces him to drive the SUV through the front window of Simeon's car dealership, where Michael gets out and proceeds to beat the Armenian to an inch of his life. Needless to say, that's the last we see of Simeon (outside an optional event, anyway).
Invoked again by the Altruist Cult much later. After Trevor delivers a fourth victim to their doorstep, the Altruists decide to include Trevor (at gunpoint) in their dinner plans. Unfortunately for them, Trevor is nothing like their usual dinner guests, and the Altruists only seal their fates by leaving an AK within arm's reach. Weasel News would later report the event as "ritual suicide" — an ironically apt description of what the cultists ended up "accomplishing".
Downplayed in World of Warcraft: The range from which NPCs attack you depends on the level difference between the attacker and the "victim". With enough levels, players practically have to walk into enemies to get them to attack. The mechanic also works the other way around, creating a powerful incentive for low-level characters to stay away from high-level areas.
In general, a PVE player picking a fight with a PVP player tends to end with the PVE player in the graveyard.
Most notable as PVE players tend towards having higher hp and judging people on that; PVP gear has lower stats, but also has a Damage Multiplier and Resistance stat for PVP. This is beyond PVPers regularly having their setup oriented towards kiting, CC, self-healing, burst DPS, and other things that make or break player-versus-player combat while PVE players just go for raw Damage throughput, and the often massive skill difference between someone who sits behind a boss smacking a macro all day and one that fights other experienced PVP Players. A PVE player seeing a flagged person with about 4/5ths of their hp and feeling mean will attempt to kill them, only for their hits to whiff, get stunned, bursted to a tenth of their hp, panic, and get killed trying to run away.
Or when a player tries to attack another player without realizing they are a higher level, have better gear, and/or very proficient with their class.
An unintentional version used to happen in City of Heroes. Certain missions would spawn an ambush waiting for the players when they exited the mission. What was supposed to happen is that the spawned mob would be at the appropriate level for the characters. On rare occasions, however, the ambush would be composed of critters of a rather lower level than the player(s). Like Level 1. Even if the player or group was level 50. This bug was in or around Issue 5. All ambushes would spawn at the minimum level available for that group (Council — Level 1, Circle of Thorns, level 5). This also lead to an unintentional spoiler for anyone who hadn't completed the level 35-40 Rikti story arc if they got an ambush, as the game would throw level 5 Lost at them.
In FusionFall, where the difference in level between you and a monster directly relates to the range at which they will become agressive. Naturally, if a monster is ten levels tougher than you are, he'll chase you down and grind you into paste, but won't so much as notice you if the reverse is true.
The Darkness has a hilarious example. Whilst walking relatively peaceful streets of New York City, the player, a mafia hitman turned world killing god of darkness with Combat Tentacles and worse, can be attacked by a simple mugger. The results are... predictable.
Deus Ex: Invisible War has this at the very beginning. You encounter a group of thugs who then threaten you into handing over some money. You are an augmented super agent, armed with at least a few guns. Leads to one of the best lines in the game. "You picked the wrong person to mug, punk."
There is another part later on that might count as this. You need to buy tickets to gain access to the laser guarded WTO HQ. The main ticket seller has been killed and replaced with a thug who grossly overcharges. You can sneak in through a vent, kill all the thugs, and press the button to deactivate the lasers yourself.
In Deus Ex: Human Revolution, during Jensen's second visit to Hengsha, Belltower is on a manhunt for him. At some point, a random punk then decides to walk up to the wanted cyborg ex-SWAT Super Soldier and threaten to turn him in if he doesn't pay up. While the option to do so exists, even people doing a hardcore Pacifist Run will likely select the "Threaten" option which prompts Jensen to give a vague threat which then causes the idiot to sheepishly back down.
Or you could give him the money, then beat him senseless and take it back.
Whenever you have to backtrack far, the wild mons hit this. "Oh my, a Level 5 Caterpie. Do your thing, Level 62 Charizard."
Although in some games, it can basically get subverted, you can run into a situation where you think it's yet another low level mon and instead it's a roaming legendary.
Also, grinding early on makes for funny situations. You can also skip some early trainers, who then say that you look pretty easy and challenge you, only to find that you have a team of Level 100's.
In Heart Gold and Soul Silver, the first Pokémon in your party follows you around on the overworld, outside of its Pokéball. This trope approaches Too Dumb to Live levels when Youngster Joey decides to take on you and your Olympus Mon.
Though since the Pokémon universe runs on Defeat Means Friendship, this trope could arguably be justified as a way of trying to make (powerful) new friends.
Fallout 2 averts this with the New Reno crime families. If you are a made man of a family, the other families will attack you on sight — unless you are wearing a suit of Power Armor, in which case they will treat you with respectful politeness.
Fallout 3 plays it straight, though. No matter how well armed, armored, and guarded by followers you may be, Talon Company or the Regulators (or both if you've been both good and evil) will not hesitate to attack you if you fast travel in certain locations. Also with one of the Random Encounters, which features what has to be the most suicidal mugger in the entire freaking universe. He will try to rob you with a shotgun that isn't loaded. Although finding this guy early in the game would have made sense, being a random encounter means you're far more likely to find him when you've already beaten half the game. You have the choice of either turning him into hamburger or telling him to jog on, and you can even point out that his gun isn't loaded, or point out the idiocy of mugging when the average raider just murders their victims for their stuff. Seriously, by the end of the game, any time pretty much anyone short of Enclave troops or Super Mutants attacks you would count as this.
If medals were being awarded for falling for this trope, though, the aliens that abduct you in the Mothership Zeta DLC deserve one. Every human living in Earth's various post-apocalyptic wasteland regions is a Combat Pragmatist out of necessity for survival, and everybody this fact gets lost on is guaranteed a swift removal from the gene pool. The aliens abduct one of these humans and place them in a containment cell with another human from the wasteland. Cue the humans working together to hatch an escape plan, free several other humans aboard the ship, massacre the ship's security forces/crew, cripple its internal defense grid, disable its death ray, obliterate its research facilities, take control of the bridge, and then use the ship's remaining weapons to destroy its escort while slaughtering any boarding parties that try to retake the ship.
Fallout: New Vegas takes this a step further with the Freeside Thugs. When you first show up, you are attacked by 2 or 3 unarmored and unwashed thugs armed only with a variety of crappy melee weapons. They pose very little threat even at low levels, yet they will attack the Power Armored wearing badass with an Avenger Minigun, followed by a Nightkin Super Mutant with a BFS and heavily modified Eyebot. They last roughly the amount of time it takes for you to decide which of the numerous means of killing them (which ranges from chainsaws to an orbital death laser) you feel like using at that moment in time. Actually, if you're well liked in Freeside they usually won't even last that long, as members of the Kings gang will typically gun down the idiots before they can even get within line of sight to you.
New Vegas also features Orion Moreno, a bitter old man living near Camp McCarran and being harassed by the NCR, who claim that he is "squatting" on "their" land, even though he built the house he lives in decades before the NCR expanded into Nevada. As it turns out, Moreno isn't just some random old coot, he's actually a Retired Badass, being a former elite trooper for the Enclave, a One-Man Army who still has his Powered Armor and minigun tucked away where he can get them. This trope is especially played straight if you complete Arcade's companion quest by persuading Moreno to fight on the side of the Legion, the NCR's mortal enemy.
Early in Return to Krondor, two random muggers attempt to rob legendary thief Jimmy the Hand — who in fact scolds them for not recognizing a dangerous mark when they see one, yet they try it anyway.
Early in Dragon Age: Origins, you come across some bandits trying to extort "tolls" from refugees. When they try to pull this on your group (typically at that point consisting of a mage, a mage-hunter, a war dog, and whatever the player character rolled as), one of your possible responses is basically "Are you serious?Look at us!" You can actually turn the situation on its head, and demand that the bandits pay up. You can, alternately, reveal to them that you're a Grey Warden. The Grey Wardens are, by the by, wanted for treason and apparently murdering the king, which you can point out to the bandits, at which point the leader will immediately crap himself, stand aside, and bid you a good day and to "continue on with your king-killing ways." And, if you're playing a mage, you can make this known to them. Cue the whimpers of "I don't wanna be a toad!"
Much later on in Dragon Age, when you've leveled up a lot more and your personal reputation has been well established, you can talk to a city guardsman named Sgt. Kylon in Denerim. Although there's still a bounty on your head for your supposed treason, he explains that even he if he believed the claims of treason, which he doesn't, he still would no interest in attempting to arrest you. "If I asked my men to apprehend you, they'd all run and cry big, sobby tears in their courtesan's bosoms and leave me all alone to be skewered." You can then discuss helping out the guards, at which point he asks you about chasing some mercenaries out of a brothel. "I said beat down, not kill. Let me make that really clear. Not on fire, or exploded, or Maker knows whatever type of grisly death you can dream up... Sorry, used to giving orders to my boys." After you successfully complete this task, he meets you halfway back to the city market area to give you your pay, only to have the leader of the mercenaries come after you in a towering rage. Upon seeing you in action, Sgt. Kylon's only response is "And people actually voluntarily attack you? Are they just stupid?"
If you imported your Fereldan Warden in Dragon Age: Origins – Awakening, any non-Darkspawn trying to kill you will pretty much be trying this out, especially Bann Esmerelle and her lackeys. From before the start of the expansion, half the nation of Ferelden led by a hero, the Antivan Crows, (a faction of) the Blackstone Irregulars, some Orlesian assassins, a dragon-worshipping cult (and their dragon), the Witch of the Wilds, some Tevinter smugglers, a forest full of werewolves, a dwarven political faction, some maleficars, some golems, some demons and Maker only knows what else have all tried to kill you and all have failed. This isn't counting the countless darkspawn that all but died by your hand, and the archdemon itself, and some ass-headed jokers from Amaranthine think they could do any better?
While going as an Orlesian Warden means you have no such accomplishments under your belt, the conspirators and everyone else are forgetting something: (1) you're a Grey Warden and (2) you're Orlesian. Orlais is known for its Deadly Decadent Court, where assassinations, conspiracies, and backstabbings are the order of the day, alongside some fancy new shoes and a cleavage enhancing dress, if we're to take Leliana's word, and you could strike back at your enemies like an Orlesian (like by taking people hostage). And being a Grey Warden is never something to take lightly, as there is a reason you were made one. And putting those aside, your first feat in Vigil's Keep is to near-singlehandedly take it back from the darkspawn, where everyone else was pretty much getting slaughtered until you pulled their bacon out of the fire.
And in Dragon Age II, if you wander around Kirkwall at night, you are routinely set on by muggers from various gangs. Sort of makes sense when you're a penniless refugee, less so when you're the champion of Kirkwall having singlehandedly dealt with dozens of threats to the city, and even less so near the end of the game when you are so ridiculously powerful that the local Knight Commander treats you with kid gloves. Noteable for being able to actually wipe out all the criminal gangs, essentially ending the problem completely. It actually sort of makes sense as the game progresses; in the first act, they're just standard bandits. But by the third act, the gangs have been replaced by brainwashed cults and slaver bands led by demons and blood mages.
In Far Cry 2 randomly encoutered enemies may cower in fear and flee when they realize that their intended target is the legendary mercenary who is said to slaughter whole camps and maim opponents just for laughs. Provided your reputation is high, of course.
NPCs may attempt to rob stores while the player is trying to buy things. Since robberies disable shopping at the store, this typically results in the thief being trapped in a small room with a very annoyed player.
Veteran Child kidnapping Shaundi and then trying to assassinate the boss. He's a DJ, the boss is a homicidal maniac.
in Saints Row: The Third, after the Saints get hit with a campaign of desprestige, you can find random NP Cs in the map, holding signs telling the Saints to Leave Steelport. Pass by them and they'll insult or even attack you. Yeah, not the smartest choice to attack someone who is known as "The Stillwater Butcher".
Notably averted in EarthBound, where enemies will actually run away from you instead of engaging you in combat if you're powerful enough. Furthermore, random encounters inside dungeons will automatically do this after the area boss is defeated, regardless of level.
This is how, after spending a thousand years asleep, your character gets his modern-day clothes. He was lucky enough to be targeted by a mugger of similar size to him.
There's also an amusing encounter in the Middle Ages: as you get ready to storm the Big Bad's castle, you are ambushed by three generic mooks, the leader of which snarls that he's going to avenge the True Deaths of more or less all of the ancient and powerful vampires you've defeated so far. As he's done enumerating them (which takes some time), his cronie wonders aloud if this is such a good idea after all...
Vampire: The Masquerade – Bloodlines includes a similar scene much later with an unofficial patch: the PC gets mugged by a member of the local gang in Chinatown down a dark alleyway, with no witnesses... One dialogue option is to Dominate him into giving you all of his money. Otherwise, he makes a good snack.
Geralt: That was pretty stupid, hiring a Witcher against yourself."
The first groupings of mooks you fight in Tales of Eternia tend to be bandits and rogue mages. Why they choose to mug a kid carrying a two-foot long bowie knife and a buckler and his buddy who clearly knows several forms of karate is a mystery.
The list of people who threaten Commander Shepard and crew and are obliterated shortly thereafter could fill a short book. In the first game, it's excusable, as Shepard doesn't have much of a reputation outside of the Alliance. In the second game, after Shepard saved the Citadel and killed Sovereign, opposing him/her in any way is probably grounds for a Darwin Award unless you happen to be living someplace really isolated (like a maximum security prison) or been in a coma. The Reapers are justified being ridiculously powerful, Cthulhu-esque ships of extinction. Others, not so much.
The best example of this in Mass Effect 2 has to be Warden Kuril of Purgatory. When Shepard goes to pick up and recruit Jack, not only does he refuse to release Jack into Shepard's custody, he attempts to capture him/her, hold him/her for ransom for the Illusive Man or sell the Commander to the highest bidder on the black market as a slave. All this while the party is still fully armed. Can you say Too Dumb to Live?
Samara's loyalty mission features a turian named Meln in the VIP area of a nightclub who will crassly proposition FemShep when she intervenes to keep him from sexually harassing (and possibly assaulting) an asari dancer. Cue Meln being punched, then thrown in the general direction of the door. And if Shepard is wearing a certain DLC outfit, then this is done by a woman in high heels and a Little Black Dress.
Lampshaded by Doctor Chakwas saying the Commander "doesn't have many enemies, alive ones anyway."
Shepard's teammates does it again if you pick the Renegade options when recruiting Jack:
Shepard: I'm offering you the chance to be my friend. You don't want to be my enemy. Garrus: They have a way of dying. Thane: There's no future in it. Samara: It is a dangerous and short-lived experience. Tali'zorah: Shepard's enemies have a tendency to die. Legion: There's a high statistical probability of death by gunshot. A punch to the face is also likely.
Wrex: Anyone who fights us is either stupid or on Saren's payroll. Killing the latter is business. Killing the former is a favor to the universe.
For that matter Jack was set upon and raped by a group of thugs. She hunted down and killed every last one of them.
Mordin Solus. Salarian doctor. Set up clinic in Wretched Hive. One of three biggest gangs tried to attack. Attempt failed. Heads left outside as warning. Mordin actually former commando. Special Tasks Group. Infiltration. Crime lord approves of his methods.
In Assassin's Creed: Brotherhood, there are randomly encountered robbers who attack Ezio Auditore because he looks like a rich nobleman (which he essentially is, to be honest) and an easy mark (which he is hilariously not). This sometimes occurs even when he's on horseback, in which case he could just ride away... but him getting off of his horse only gives him more varied ways to butcher them. Worse yet for them, they somehow all have various baubles, trinkets and items he could make use of...
It only gets worse for the poor sods when Ezio starts recruiting Assassin apprentices, and as a result can wipe out the entire ambush party with a wave of his hand and a flurry of Hidden Blades or a storm of unseen arrows. (According to the community manager the apprentices are actually tailing Ezio discreetly, so they're actually ambushing the would-be ambushers.) It's implied by the Thief Assignments (or rather that completing them all causes the attacks to cease) that the robbers are from the Cento Occhi ("Hundred Eyes") gang in Cesare Borgia's employ, though none of them seem to recognize Ezio as an Assassin despite him (and his apprentices) being the only one(s) in Rome to "show their colors."
In the second sequence of Assassin's Creed IV: Black Flag, it's more like "Mugging the Monster's Friend". A pickpocket assails Stede, who looks like an easy mark, unaware that the mark is an associate of Edward Kenway, a hardened privateer-turned-pirate. The pickpocket doesn't live to regret his folly, and Edward lampshades this after killing him.
In Mount & Blade, several of the unaffiliated wandering parties (read, bandits) can and will do this. The game seems to only read party size and occasionally the quality of troops in said party as the trigger for whether the bandits will pursue or flee from the player. This can lead to situations where Looters (the weakest NPC in the game, even below the much-abused peasant farmers and villagers), will attempt to pursue a lone player whose weapon alone is worth more than the belongings of the entire Looter party combined wearing armor that ignores an overwhelming percentage of the damage done by the Looters' bottom-tier weapons. Seriously. A handful of stones and a stick versus a guy in plate armor carrying a Sword of War. You might almost pity those Looters.
Occurs in the advertisement for Hybrid Heaven. The first page shows a little old lady about to be mugged. The next page shows the lady walking away from the mugger's remains.
Happens quite often in Red Dead Redemption. Even when people recognise Marston in the streets and his name is considered synonymous with badassery, people still love trying to mug him.
Then in Knights of the Old Republic II: The Sith Lords, the Protagonist was quite content with fading into obscurity, in planet Bumfuck Nowhere located in the middle of Force knows where in the Outer Rim. The Protagonist had, by this point, a kill count more adequately counted in the thousands. So what do the Sith do? Attack her, of course, because she's the Last of the Jedi! All of them end up predictably dead in the end.
In Kingdoms of Amalur: Reckoning, it's justified since the various bandit gangs in Amalur have no way of knowing their lone mark is a Back from the Dead badass capable of beating them to death with their own Fate. It does get a little ridiculous if you happen to be completely decked out in full Prismere gear.
Khelgar Ironfist's backstory in Neverwinter Nights 2 features him picking a Bar Brawl with a group of what turned out to be traveling Sun Soul monks. Mainly because they were (in his mind) insulting the establishment by drinking water. (Yes, he was somewhat inebriated at the time.) Long story short, they beat the crap out of him. Ironically, this inspired Khelgar to try and become a monk himself.
In Police Quest II, when Bonds is pursuing Bains in Steelton Park, you encounter a mugger who will mug you with his bare hands. Radioing your partner will scare him away and get arrested.
In Max Payne 3 Max gets a gun waved in his face by the punk son of a mob boss, who gets killed shortly after. He later gets robbed by a bunch of favela gangbangers and lets them do so for some reason or another. Later on he meets them again and kills them all. In fact, this happens a lot due to Cutscene Incompetence.
Featured in trailers to The Secret World, in which the representatives each faction are attacked by minor demons and easily fight them off. Arguably the best example of this crops up in The Illuminati trailer: in this case, Alex McCall is attacked in a pub bathroom by a tentacled monster; despite being less than three feet away from the creature McCall doesn't even step away from the urinal, distracting the monster with an illusion before obliterating it with a blast of chaos magic. Cut to black, as McCall finally zips up his fly and leaves.
Entirely possible in Sword of the Stars. Admittedly in the first game war is the default option and you must opt in to ceasefire or better, but in the second game you default to neutrality and due to Artificial Stupidity other factions are still very likely to declare war without considering that you might be much more powerful. It's not uncommon for the AI or an inexperienced player to stumble upon a fledgling colony as first contact, think the owners are easy prey and attack... only for a fleetful of dreadnoughts to pop up shortly after from the dozens of developed systems the owner really has, seeing red.
Ingress: When 855 needs a new gun, he just goes and gets mugged.
The AI in Escape Velocity Nova is mostly smart enough to avert this. Mostly. Occasionally you get something like an AI-controlled pirate Viper (a light Star Fighter) attacking a player-controlled Starbridge (technically a freighter).
In Fire Emblem Awakening, a group of slavers decides to attack Noire, a seemingly timid Shrinking Violet looking for her mother in the wilderness. The party comes by to bail her out, but before they can even reach her, Noire reveals she has an Ax-CrazySplit Personality and, since the slavers were considerate enough to leave a bow within reach, she promptly starts murdering them long before any assistance can reach her.
Also happens in Fire Emblem: The Blazing Sword when a pair of bandit twins and their band of thieves decide to mug a well-to-do traveller in the middle of the desert. Only problem is that traveller happens to be the famous sage Pent, who is one of the strongest characters in the game up to that point (more than capable of taking on the entire map on his own, if you let him).
In Final Fantasy II, Leila offers you a ride to Deist. After you get into open waters, she summons her crew to attack you. After a rather easy battle, she wisely joins your party.
Beyond: Two Souls has an instance that is less Mugging the Monster than it is Mugging the Monster's Friend. Four Jerkass teens with a video camera and a baseball bat decide to beat up Stan, a defenseless homeless man, For the Lulz. His newly-made friend Jodie - who has had CIA combat training - intervenes. Firmly. The "fight" is made all the more satisfying by the fact that it's caught on the thugs' own camera.
In PAYDAY 2's GO Bank heist, one of the random events has a blackmailer call and demand a cut of the loot or he will call the police. Which might be a concern for the average bank robber, but these are the Payday Crew, for whom gunning down dozens of lawmen is just another day on the job. Fortunately for the idiot, he isn't actually rendered as anything more than a voice, or his fate would have been dire indeed.
One of the Team Fortress 2 comics features a man trying to rob a "nerdy German tourist", only to get knocked unconscious. When he wakes up, he discovers that the Medic has taken out his brain and put it inside a jack-o-lantern.
The Medic: Welcome to your new life! As a Halloween decoration!
The game's AI was specifically coded to try to avoid doing this; the AI will not attack a stronger opponent unless it has some kind of advantage over them. It still happens, though, as the AI is sometimes not a good judge of who a stronger opponent is. For example, it may try attacking a civilization with a small amount of standing military forces, only for said civilization to very quickly build or purchase a far superior army, or simply out-produce the AI with a superior industrial base and overwhelm it with numbers.
In the backstory, the Drengin were at least Genre Savvy enough to get someone else to try mugging the monster in question. They convinced the Xendar that the peaceful, diplomatic Terrans would be an easy conquest, so they could judge the Terrans' strength in war. End result: the Xendar were fought all the way back to their homeworld, at which point the Drengin hurriedly wiped them out before the Terrans could figure out who put the Xendar up to this.
You can invoke this in one of the Velocipede Squad options, disguising yourself as a mere drunk and letting people think they can rob you. Since the Velocipede Squad requires you to be a certified badass to join, these people are easily trounced and battered to hell if they so much as breathe on your pockets
Naturally, you can end up doing this yourself, usually when failing challenges and finding out your target was a bit sneakier, smarter, or stronger than you thought. Examples include getting thrown overboard by a docker's hidden help and trying to give the Minister a beating only to find out the chap used to be a very good boxer.
The entirety of London ended up doing this when they tried to invade Hell, and found out the Devils not only are more or less endless, but they also have anachronistic weaponry that trounced the Empire's own three times over.
And of course, the Devils themselves end up doing this when they try to sack Polythreme, which is an insanely active Genius Loci to the point any inanimate objects within it gain a life of their own that acts both individually and like a Hive Mind with the rest. One can only imagine the faces of the devils as their own ships, weapons and even clothes decided to stop cooperating and turn on them.