I've always been uncomfortable with pet shops that seem to have too many large cichlid species, arrowanas, bichirs, etc. In reality very few people can house these fish appropriately, and it seems like a firm commitment to supporting bad aquarists.
But absolute shame on pet shops who carry iridescent sharks, red tail catfish, pacus, true tank busters that should never be available in a neighborhood retail pet shop. I really feel that one should have to go to the trouble and expense of supporting a specialty boutique for these kinds of fish.
In the saltwater section, I feel bad when I see seahorses or mandarins (and related dragonets). They look great in the pet shop, and may even pick at a little food. But they will die on a near-term timeline unless the aquarist is culturing nutritious live foods.