Wolves???
The dire wolf was the heaviest canine known to have existed, and was still around at least as recently as 7500 BC, meaning it coexisted with PreColumbian humans. The dire wasn't an awful lot larger than the largest gray wolf of today, so it probably wasn't significantly more of a threat -- nevertheless, still dangerous. There's actually some researcher (or perhaps more than one) who wants to revive the species using surviving intact DNA. I consider that to be not that great an idea.