How many wolves could kill a tiger?

In practice, none: wolves are locally extinct in the range of the Siberian tiger.

Maybe Siberian tigers are extinct in the range of the wolf?
- Wikipedia has further details:
  Tigers depress wolf (Canis lupus) numbers, either to the point of localized extinction or to such low numbers as to make them a functionally insignificant component of the ecosystem. Wolves appear capable of escaping competitive exclusion from tigers only when human pressure decreases tiger numbers. In areas where wolves and tigers share ranges, the two species typically display a great deal of dietary overlap, resulting in intense competition. Wolf and tiger interactions are well documented in Sikhote-Alin, where until the beginning of the 20th century, very few wolves were sighted. Wolf numbers may have increased in the region after tigers were largely eliminated during the Russian colonisation in the late 19th century and early 20th century. This is corroborated by native inhabitants of the region claiming that they had no memory of wolves inhabiting Sikhote-Alin until the 1930s, when tiger numbers decreased. Today, wolves are considered scarce in tiger habitat, being found in scattered pockets, and usually seen travelling as loners or in small groups. First hand accounts on interactions between the two species indicate that tigers occasionally chase wolves from their kills, while wolves will scavenge from tiger kills. Tigers are not known to prey on wolves, though there are four records of tigers killing wolves without consuming them. Tigers recently released are also said to hunt wolves.
By any chance, are Siberian tigers responsible for that?
- Evidently: in regions where humans have eliminated tigers, wolf populations have started to appear.

Individually? None.

Well, also 1 wolf could be enough to kill a tiger, depending on the circumstances, adult wolf, baby tiger? Tiger is comatose?

I only ever see them in the same place at furry conventions, but that never seems to be what they're interested in doing

UwU this poor wittle tigey-wigey is surrounded by big bad wolfies. I wonder if it's enough to bring me the little death that I swell and ache for...

It's important to remember wolves are pack animals so they would coordinate. Depending on the weight difference I think it could be as few as three

Recalling the videos of a single male lion pretty much ripping apart a pack of hyenas... Tigers are even bigger and stronger than lions, and wolves don't have anywhere near the bite force of a hyena. I think you'd need a lot more than three.

I think 5-7

Tigers (all predators) are weak to non-frontal attacks. Wolves attack in groups. The tiger would kill 2-3 frontally, but suffer damage and blood-loss at its flanks and hindquarters. Then it becomes a matter of finishing the job.

In any fight, circumstances are king. You need far, far more variables defined in order to be able to answer this question, and even then it won't be a certain outcome. Who has the element of surprise? What's the age, weight, and sex of the tiger (and the wolves)? How recently have the tiger/wolves eaten? Does anyone slip on a banana peel during the encounter?

Maybe we're going about this wrong. Are you trying to make sure the tiger is dead or are you trying to use as few wolves as possible?

Does anyone slip on a banana peel during the encounter?
You made my day. The Tiger in my imagination: https://youtube.com/watch?v=H5MduYLe2lA&t=158s
Good specimens in my private coliseum

About 19 undecillion should be enough