the pokedex entry for excadrill says that their digging can be destructive to subway tunnels...that would be bad.
and gigalith says their attacks are "strong enough to blow away mountains", that must be bad because if they blow away an entire mountain, the rocks have to land somewhere, so its entirely possible for them to blow the rocks somewhere destructive like onto someone's house or something.
i'm sure both of these things are "accidental" and unintentional in the case of the wild pokemons, although, i would think trainer using a pokemon doing these things should be held accountable for it
of course, those are gen5 pokemons, considering this is the gen6 message board, should we keep the discussion about gen6 pokemons? --- Morrie's Monster Pit was banned on 3 continents because you could see his junk....