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Chinese mastiff and AKC or show Tibetan mastiff can never do that, do-khyi has working ability but not enough power. But native breed Tibetan mastiffs in Tibetan plateau and Nepal tibetan villages can actually do that. But if the dog has to fight a leopard, he is given a metal collar with spikes so that he isn't injured. Two can fight a tiger, 3 can kill it without protection. One dog can take on 2 wolves. (I am talking about TMs in Nepal and Tibet not do-khyi (20-26 inch) smaller dogs found in India also.( Named as Indian or Himalayan mastiff by some)
2 or 3 should be able to do the job, dogs as big as donkeys, bite force of around 500PSI, ridicolous stamina and strength, and there are stories of chinese soldiers shooting the dogs and the thing still fights. Now, for the people saying that no dog can take on a lion or tiger, take a look at the kangal and caucasian shepperd

Feline fanatics tibetan mastiffs have tough skin and fur which protects them so the tiger cant just kill them in seconds also while the tiger attacks one tibetan the other one or two will attack a vulnerable area wounding the tiger or fatally killing it by getting its neck but your other mastiff will need medical attention and rest as it will be severely wounded

Any moron that says they can even defeat a leopard has no zoological background. The answer is no. Example if you put 3 tibetin mastifs in a huge care with either a leopard, cougar, lion, jaguar, or tiger. They woule stand no chance. Every one of them either weighs around 1 of them or more. A big cat is far stronger and would end them faster than they have a chance to do anything. Especially if it were a lion, tiger, or jaguar. The 3 bigs of the cat world. And dont let the jaguars size fool you. Although it is not as large as a lion it is far stronger. It is the strongest big cat pound for pound and has the second largest bite forr of any land mammal, 2000 to 2100. Only the hiena has a higher bite force at 2200. I would rather take my cances with the lion. And the tiger is not even a conversation. Honestly none of the big 3 are.

The only thing the tiger would see is a hot dog for lunch