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.
In InuYasha, one of the youkai him and his group encounter is a giant, manipulated wolf and his normal-sized pack. Later they encounter a village where everyone has been slaughtered by wolves, lead by a humanoid wolf-youkai named Koga. Eventually Koga turns out a Jerk with a Heart of Gold and they (usually) get along fine with him.
A Dracula Lives story featuring Solomon Kane has Dracula saving the man from a pack of wolves before inviting him to his castle.
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.
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.
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.
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.
During the "War of the Five Kings" in a A Clash Of Kings an enormous pack of wolves, possibly numbering in the hundreds, is roaming the Riverlands under the leadership of a fearless direwolf, presumably Arya's former pet Nymeria. The pack has grown stronger by the events of A Dance With Dragons.
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 pelt 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.
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 World of Warcraft, 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.
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.
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.
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.
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.
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).