This is a curse or a bad player and this is against who a play is profitable. You will be able to identify a fish for their lack of strategy and the moves they make towards the negative expected value. These kinds of players will bet too much and play marginal hands.
The opposite of a fish is a shark and this is the player who will rob the fish of their money. As for the players who are in between, these are barracudas and they still make their money from the fish. As for the aggressive players, they are known as piranha. When a table has plenty of players who are bad, the table is known as an aquarium.