The corydoradinae do not have permanent teeth as we understand them, or as fish like the characins (tetra, etc) do. Premaxillary teeth only occur in fry and juveniles and these are then lost since the fish does not need them due to its benthic feeding. So any fin damage is not due to a cory, ever. Plus, I have never heard of a "mean" cory, though one may exist somewhere I suppose; but this has to be the most docile of fish.
As someone mentioned, Corydoras panda is one of the most sensitive species, notwithstanding the fact that they are now being commercially raised. One often expects wild caught fish to be more fussy.
I would get more, but be very slow with acclimating them. This is one of the most social species; mine are together almost all the time.