Water.
Not really as a killer whale would keep a natural balance in an ecosystem.
Orcas, also known as killer whales, are the main predators of whales in the ocean ecosystem.
Orcas or killer whales have no natural predators.
Killer whales
Killer whales
They keep the ecosystem in balance and killer whales and some sharks feed on them.
Natural predators of Killer Whales include larger sharks such as Great White Sharks and occasionally larger Killer Whales. However, adult Killer Whales are typically considered apex predators with few natural predators due to their size and strength.
All mammals have some sort of predator prey relationship. The only natural enemy to whales is the orca (the killer whale in question), other than that, whales have no NATURAL enemies.
killer whales
The killer whale has no natural predators other than man.
Killer whales are top predators in the sea. Healthy adults have no natural predators, but sharks prey on older, younger, or ill killer whales.
Killer Whales eat Great White Sharks. Nothing eats Killer Whales unless they are already dead from natural causes then everything is free to take a bite.