Yes, but not without contest. Other types of predators existed at that time as well, including other megatooth sharks ( The Group that included otodus and others) The Megalodon had to contend with other sorts of life, as do great white sharks today. Take livyatan for example. It is of a similar size and had teeth over a foot long. read more
It is very likely that megalodon was the apex (top) predator in its ecological niche. Apex predators don't have other natural predators. Of course, we don't have a complete fossil record, and it is possible that megalodon had predators. read more
However, an adult Megalodon is a different matter altogether. Not only its extreme size is an anti-predator strategy in itself (Pimiento et al., 2010) but the animal is an endothermic (Ferrón, 2017) raptorial superpredator (Wroe et al., 2008) with extensive hunting experience at this stage. read more
C. megalodon was the top predator of its time and it is believed that it ate whales, dolphins, squids, fish, and turtles. It hunted almost everything else that lived in the oceans of its time. read more