As alpha predators and clever pack hunters, wolves have often been feared and hated by humans. They frequently preyed on human livestock and, in Europe, humans themselves to the extent that serious efforts were made to wipe them out of the region. This reputation bled over into fiction where wolves were portrayed as nasty, savage and rapacious predators seemingly bent on devouring everyone they could. Give them some intelligence and they'll be cruel, nasty and sadistic.
Because wolves are pack hunters, this makes them even more dangerous. One wolf is easily capable of killing an unarmed human, but bring out a dozen or so and suddenly they can devour anything in their path, especially the ill or weak humans we want to protect most like women, children and the elderly.
Note that while this trope usually comes in the form of a pack of wolves, it can equally apply to a lone one. Bonus points if it's much more dangerous and persistent than a single wolf has any right to be.
Compare and contrast the more recent trope Noble Wolf, which features wolves as noble, proud, reasonable or even outright heroic. When the two tropes intersect, they will still be very dangerous and not to be underestimated or disrespected.
See also The Big Bad Wolf and Hellhound. Compare animals that share similar reputations, such as bears and sharks.
One episode of Pokémon portrays a pack of Houndour like this. However, it becomes Subverted when it's revealed why.
The Wolf in Chirin No Suzu. Ruthless and vicious, he kills whatever he can sink his fangs into — including Chirin's mother. Subverted because Chirin soon grew fond of the Wolf, seeing him as a father. In fact, near the end, after killing Wolf, he soon felt sad and realized that revenge wasn't satisfying.
In an early storyline, the normally friendly wolf youkai Royakan is unwillingly transformed into a monstrous, berserk beast that can vomit up packs of equally vicious normal-sized wolves.
A later storyline introduces a whole tribe of wolf youkai, infamous for eating humans and destroying entire human villages in the process. Led by the humanoid wolf youkai Kouga, these wolves destroy three human villages (including Rin's, killing everyone there including Rin herself) before encountering Inuyasha's group. By the end of this first encounter, however, Kouga becomes enamored enough of Kagome that he forbids his tribe from attacking humans and they become Noble Wolves instead.
The wolf shown in the beginning of the film/comic 300 is depicted as demonic and threatening.
Kyle Abbot from 52 and Batwoman. A werewolf shape-shifter who worships crime. He becomes disillusioned by his peer's interpretation, and breaks off into his own sect, the true believers. He's an occasional ally of Batwoman.
A Dracula Lives story featuring Solomon Kane has Dracula saving the man from a pack of wolves before inviting him to his castle.
Idées Noires: One gag has a man lost in the snow wandering around thinking he is doomed. Then he sees lights in the distance and thinks it's a city, but it turns out to be the Glowing Eyes of Doom of a group of wolves.
Fenris from the Lucifer comics manages to take revenge for his fellow mythologies by stomping into a story arc almost entirely populated by Judeo-Christian characters and instantly becoming one of the most threatening antagonists. When one challenges him for this he points out that before humanity cowered before demons they feared the wolves beneath the trees, proceeding to become the Big Bad through raw Badassery.
The Secret of Kells, when Aisling sics her wolves on Brendan as he's traveling through the forest in search of oak galls. Later inverted when Aisling sics them on the Vikings that are about to kill Brendan and Aidan in a Big Damn Heroes moment.
Frozen features a scene in which the heroes are pursued by a pack of wolves similar to the Beauty and the Beast example.
Film - Live Action
White Fang - For a Disney film, the scenes where the characters are being hunted by a pack of wolves in the opening 20 minutes or so is almost downright terrifying.
In Never Cry Wolf, another Disney film, Tyler is at first afraid of the wolves and has a nightmare about being chased by them. Subverted when he actually meets the wolves, and they're nothing like that.
A pack of mystic wolves are the main antagonists in Wolfen.
The Grey: The survivors of a plane crash in Alaska not only have to survive the elements, but survive the pack of wolves that is chasing them down.
Frozen: Wolves take predatory interest in Dan after he jumps from the ski lift and breaks his legs.
The name of the eponymous protagonist of Lone Wolf McQuade is clearly supposed to invoke this.
In the third Riddick movie, a wounded Riddick wakes up after being left for dead on a barren planet by the Necromongers. He is quickly sighted by a pack of alien wolf/dog creatures who pursue him. Subverted later on when he discovers a lone pup, whom he eventually raises to become a loyal companion.
As the cast of Day of the Animals sleeps peacefully after their first day of backpacking, a lone wolf suddenly attacks Mandy and scars her face badly. This forces her and her husband Frank to split up from the others to get to the local forest ranger point.
Inverted at first in The Fifth Elephant then played straight after the wolf who's keeping them in line dies and they revert to their natural instincts, which include killing any werewolves they come across, (even Angua). She doesn't begrudge their hostility though, she knows and accepts that they have some pretty good reasons to hate werewolves.
J. R. R. Tolkien liked this one. Packs of intelligent wolves (called Wargs) threaten the main characters of both The Hobbit and The Lord of the Rings. However, Tolkien does make a distinction between regular, rarely dangerous wolves, and the decidedly more monstrous Wargs, who always directly serve the bad guys in his legendarium.
In The Silmarillion the father of werewolves Draugluin (Sindarin for "Blue Wolf") appears, as does their most terrible offspring Carcharoth. Sauron briefly takes the form of a werewolf to fight the wolfhound Huan.
In a story by Saki, two men, the heads of feuding houses, are badly injured and trapped in the woods. No sooner do they decide to put their differences aside do they hear a rustling in the bushes. One man can see their presumed rescuers coming. When the second man asks if they are his men or the other man's men, the first man answers with one word. "Wolves."
The Dresden Files: While he's watching the Alphas in action Harry notes that, in this age of guns and helicopters, humans have forgotten why we used to be afraid of wolves, and that there are several very good reasons.
The Wolves of Willoughby Chase: Im an alternate England where packs of wolves roam the 19th century Yorkshire countryside, the young heroine is almost killed when one such pack attacks a train. She's only saved when the man sharing her carriage stabs the wolf that's got in with them to death.
In A Song of Ice and Fire, most wolves are considered Savage Wolves, but the direwolves adopted by the Stark children vary according to the personality of their owner and how well they're trained. Among the most savage are:
Shaggydog, Rickon's direwolf. He is untrained and is as feral as his owner. He is known to attack unprovoked, and bites Maester Luwin and pounces on Big and Little Walder when they hit Rickon during a game.
Nymeria, Arya's direwolf. She was originally well-trained, but since being driven off early in the first book, she has gone feral and now leads a huge pack (numbering in the hundreds) of ordinary wolves which threaten both livestock and man throughout the Riverlands.
There's also Grey Wind, who belongs to Robb. While not wild or uncontrollable, he rids beside Robb into battle. He quickly becomes The Dreaded, with people talking about a huge wolf tearing men and horses apart.
The boys go hunting for food, and run into a wolf. You'd think it would easy for four of them to take down one single wolf, but it's not. They are helpless until the dog, Maxie Jr., shows up to distract the wolf, at witch point they gain the upper hand and kill it. Later on, when they need wolf pelts to survive the snow, they go looking specifically for more wolves, and find a whole family in a cave. Although three of them plan to take on the entire cave (which would have been suicide), some Divine Intervention from Sol comes in the form of a lightning bolt that kills most of the wolves, leaving only three for the humans to fight.
The antagonist, Loki, also takes the form of a crimson-colored wolf. He is not seen with any other wolves, but attacks Mickello directly once every year in an attempt to kill him or injure him.
In Dan Abnett's Gaunts Ghosts novel His Last Command, Gaunt remembers how Colm Corbec would tell stories of wolves circling "the stranded, the unlucky, the lost" to bring them down; his current situation, being stalked by an unseen Chaos creature, reminds him.
As when a prowling Wolfe, Whom hunger drives to seek new haunt for prey, Watching where Shepherds pen thir Flocks at eeve In hurdl'd Cotes amid the field secure, Leaps o're the fence with ease into the Fould:
In White Fang, wolves are presented as harsh and savage, but the hero, being part dog, eventually rises above his instincts to become "tamed"... After being forced into dog-fighting along the way, although "fight" is not accurate - "execution" comes closer. It got to the point where they had to tie him up for the start of the fight, otherwise he'd kill the other dog before it had finished its preliminary snarl-and-threaten routine. Once the dog had finished its routine, it would almost certainly not be any more merciful.
A Wolf In The Soul contains extensive descriptions of wolves on the hunt. Greg vs. geese is one somewhat graphic example; another is Greg's wolf's pack vs. its father's pack.
The eponymous villain in Brokenclaw keeps caged wolves at his mansion so that he can feed people who have disappointed him to them.
In Willa Cather's My Ántonia, a couple of Russian immigrants narrate an incident from the old country, where a bridal party driving sledges at midnight in winter was attacked by a large pack of ravenous wolves, with extremely horrific results.
Zigzagged with Alpha for three books in Survivors despite him being part wolf. He rules over the Wild Pack with a strict yet firm paw on one hand, but he's also a bully and racist towards pets and Fierce Dogs on the other. Finally, this trope gets played straight in The Endless Lake, where Alpha fakes his own death and joins the Fierce Dogs as their Omega, thus betraying his pack.
In the Doctor Who episode In The Forest Of The Night, a pair of wolves hunt Maebh. Then they catch up with the gang... and run past them, ignoring them. Turns out they weren't running after her, but away from the tiger!
Fenris, the giant wolf fated to devour Odin himself.
Fenris' sons, Hati and Skoll, who are destined to devour the moon and sun.
The negative perception of wolves is directly responsible for the modern Swedish name for wolves: varg, meaning "killer" or "strangler". Folklore had it that saying wolves' proper name (ulv) would call them, or at least cause bad things to happen, which lead to wolves being called what they were seen as (murderous brutes). Problem was, this became so wide-spread and went on for so long that varg ended up as the proper name for a wolf, and the folklore about speaking their name being bad remained.
One of the symbols of Ancient Rome was the wolf. This grew out of legends that Romulus and Remus, founders of Rome, were literally Raised by Wolves. However, contrary to modern perceptions, they didn't adopt the wolf because of any inherent "specialness" attributed - they hated the animal just as much as everyone else around them. Rather, the story is symbolic of how vicious the Romans saw themselves to be.
In Inuit mythology, the Amarok/Amaroq is a giant wolf who hunts in solitude, specifically picking off people foolish enough to hunt alone at night. Sometimes an Amarok plays the role of a Noble Wolf instead, but is usually treated as a villain.
"Peter and the Wolf" depicts the titular wolf as a the primary antagonist, with him eating one of the other characters and attempting to eat the rest.
While Dungeons & Dragons depicts wolves themselves are depicted as morally neutral and they are even available as companions for heroic characters, the monstrous Worgs (taken from Tolkien's "Wargs") and Winter Wolves are invariably evil and dangerous.
Traveller The Vargr are wolves and other canines genetically engineered by the Precursors . They are great merchants and pirates, but they are incapable of organizing and so aren't as effective in a straight fight as humans.
Madfang Ragewolf from Patapon 3 is one of the main antagonists of the game. He is linked to an archfiend and represents the Deadly Sin of Rage.
Spiral Knights has Wolvers, they are quick, depending on the breed can inflict status effects, and if they're accompanied by an Alpha, their attack increases, players will often be killed by a pack of wolvers at least once in their in-game life.
In Red Dead Redemption, wolves are tough, highly aggressive, persistent, have a knack for showing up precisely when you don't need them do, love to kill your horses, and attack in waves. You gun down four or five of them, look around, and the coast seems clear, only for another batch to arrive just as you put your gun away.
In Dragon Age: Origins you'll occasionally run into packs of wolves as enemies. There's even one specific encounter on the overworld map that can be especially vicious on higher difficulties, a rare form of That One Random Encounter.
In Skyrim, it's not uncommon for a player to find themselves attacked by two or three wolves at once. They're easy to kill, but they can become Paranoia Fuel if you can hear the howls but are unable to see them or know the direction the howls come from. The worst part of the wolves is that they may infect you with Rockjoint plague which severely reduces your fighting ability.
Cataclysm: Wolf packs are one of the worse non-zombie threats roguelike. They're made all the worse by the fact that their letter color can make them very hard to spot before they're on top of you.
In Minecraft, wolves normally mind their own business, and can even be tamed and used as guard animals but if you attack a wolf, it and its whole pack go berserk and try to kill you.
MediEvil: Latter portion of the cemetery stages feature wolves. In order to leave the cemetery, you have to fight two stone wolves which guard it.
In Age of Empires II, Age of Empires III, and Age of Mythology, wolves are the archetypical wild predator of the wilderness. If Age of Empires II is played without the expansion, wolves are the only predator in a game, that ranges geographically from Europe to the Middle East, to Asia. Age of Mythology is also the only game of the series where wolves can be hunted for food, otherwise they are just a menace deadly to villagers.
Back in I and II, wolves were one of the Barbarians' recruitable creatures (stronger than both goblins and orcs). In both of those games, Barbarians were defined as an Evil town...
Gothic: Wolves, and other creatures in the wolf family, can be dangerous depending on your level, because unlike with most other enemies, it is difficult to lure them to you one at a time, so you'll usually have to deal with entire packs.
Tomb Raider (2013) often features packs of wolves attacking you. Even worse, one level has you enter their den to get supplies.
The early stages of Tomb Raider also had packs of wolves trying to kill you.
The final boss of Suikoden II, the beast rune, which is shown to be the embodiment of feral and murderous evil, is presented in the form of a massive, two-headed wolf.
Many Wolf-type enemies have an ability that causes them to howl and alert other nearby wolves of the player's presence, effectively swamping you if you're not very careful.
There's the Worgen, such as the Sons of Arugal, original members of the Druids of the Pack, and the Gilnean Worgen (which are playable). Heck, one such Gilnean Worgen picks up a STAGECOACH and starts BEATING PLAYERS WITH IT.
Goldrinn...goddamn, Goldrinn. Goldrinn revered as a minor god for good reason. Even the Orcs respect the Wolf-God (though they call him Lo'Gosh). The guy is best known for possessing King Varian Wrynn, being utterly wrathful, being the source of the Worgen curse, and tearing out the throats of legions ofBurning Legion demons.
Played with in Tasakeru, where wolves are one of the eight sentient species. The other species think they're scary, primitive, carnivorous savages, but they're just following very old traditions.
Neopets - While the pirate Captain Scarblade is a savage pirate, not all Lupes, a wolf-like species, are evil or vicious.
The Wolf Apocalypse in Gunshow, which was caused by God who had forgotten Jesus's birthday, and was trying to make it up to him.
In No Rest for the Wicked, the woods are known to house wolves, which is why Perrault refuses to believe that November came through the woods alone. However, the actual wolves appear only as skins in Red's cottage.
Reynardine falls under this indirectly, even though he's actually a fox. Since possessing Annie's wolf doll, he seems to be undergoing a slow Heel-Face Turn - in particular, he's noticeably less of a "jerkface" when he takes the form of a full-sized wolf, rather than his usual pint-sized plushy form.
Metalocalypse - the band's therapist tries to attack them but falls out a window. He survives the multi-story fall, but then gets his arms ripped off by wolves who live in the compound (though he survives that and gets a new pair of mechanical arms).
In the episode of The Simpsons called "Cape Feare", grandpa Simpson is in front of the Simpson house and says "I'm cold and there are wolves after me" (cue scary howl... in the middle of the day). Also, in one episode, Groundskeeper Willy goes mano-a-wolf-o with an escaped Alaskan timber wolf, "Whose jaws can bite through a parking meter." He beats it.
It's been widely reported that in WWI two armies of German and Russian soldiers signed a temporary ceasefire in order to fight off hundreds of wolves that tried to eat them. It's unknown if this is true but there were some incredibly violent wolf attacks during the Great War caused by all the environmental destruction happening at the time.
While very few wolf attacks have been verified in the US and Canada, wolves in Europe and Asia are far more aggressive, particularly in Europe after the 13th century when the buildup of dead bodies caused by the Black Death allowed them an easy source of food, giving many a taste for human flesh and a habit of frequenting villages, city outskirts and major roads in the process. Special structures were reportedly built along highways for travelers to take refuge from roving packs in.
And of course, rabid wolves are exactly as dangerous as their domesticated counterparts.