* Largest by size: The Sperm Whale is the largest toothed whale and the largest predator by size. It can reach up to 67 feet long and weigh over 45 tons.
* Largest by weight: The Blue Whale is the largest animal on Earth, reaching up to 100 feet long and weighing up to 200 tons. While it primarily feeds on krill, it can occasionally eat small fish and squid.
* Largest by sheer numbers: The Antarctic Krill is technically a predator, feeding on phytoplankton and other small organisms. While not a single individual predator, the sheer abundance of krill makes them a dominant force in the food chain, consuming massive amounts of phytoplankton and serving as a crucial food source for many other marine animals.
Therefore, depending on your criteria, the biggest predator in the sea could be the Sperm Whale, the Blue Whale, or the Antarctic Krill.