Fierce fish are a type of aquatic animal known for their aggressive behavior and sharp teeth. The term can refer to two different species: the Piranha, which has seven letters, and the BARRACUDA, which has nine letters. Piranhas are a species of freshwater fish native to South America, and they are known for their sharp teeth and aggressive behavior. Barracudas are a species of saltwater fish found in tropical and subtropical waters, and they are also known for their sharp teeth and aggressive behavior.