Not sure about all of Equestria. We've seen a gray copy of Big Mac in this episode, for example, and this one can be just as strong as Big Mac.

In Ponyville there is a Bulk Biceps too, but he is a pegasus. Still, we don't know it yet: how he compares to Big Mac in terms of strength...

Celestia is probably the physically strongest pony of all time (she is an alicorn and she is the biggest one of them).

Luna had already demonstrated her great strength by breaking the ground beneath her hooves in " Luna Eclipsed".

Since Cadance and Twilight are an alicorns too, it is only natural for them to be very strong.