The largest shark that ever lived, the prehistoric, and certainly extinct megalodon, might have been driven to extinction by a smaller and nimbler competitor that still roams the seas today (aka) the great white shark.
Research pegged the behemoth's extinction to around 2.6 million years ago. It's length reached 15-18 meters! It was the biggest shark ever known.
The megalodon went extinct because of smaller competitors that ranged the ocean too that also challenged it face on. Awhile later it went extinct and fossils have been found of many animals but they are still unsure of how big the megalodon is.