Well, it depends what you mean by buffalo. In the most accurate sense, a “buffalo” is a member of the bovine subtribe Bubalina. Going by that definition, the largest-ever modern buffalo would be the wild water buffalo, which can weigh up to 1,200 kilograms.
However, if we consider extinct species, there were possibly larger buffalo. The identity of the Pleistocene bovine Pelorovis (left) is still poorly understood, but some suggest it was related to modern buffalo species. In any case, it weighed a massive 2,000 kilograms, partially due to its spectacular horns, each as long as a man is tall.
However, in North America, a “buffalo” is a species in the genus Bison, zoologically referred to as a bison. If that’s what you meant, then the American bison would be the largest of extant species, which can, on occasion, attain weights of 1,724 kilograms - albeit on farms where they are well-fed and cared for.
Again, when we include extinct species its crown is lost - this time to the so-called long-horned bison, Bison latifrons. With weight estimates of up to 2,000 kilograms, it competes with the aforementioned Pelorovis for the title of heaviest extinct bovid.
And… *sigh*… technically there’s a genus of fish called buffalo, Ictiobus. I almost know for a fact that you weren’t referring to them, but just to maintain accuracy, the largest buffalo fish are bigmouth buffalo, the largest of which reach lengths of 1.23 metres and 29 kilograms.
So there, WHATEVER you meant by buffalo, I can say that I’ve answered the question correctly. I might as well close with one of my favorite sentences of all; "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo". And yup, it is grammatically correct.
