Hina, Garp and others were in a conversation when Garp told us about Rox pirates, who were the rulers of the sea even before Gol D. Roger’s era and about 40 years ago. So, Rocks pirates used to rule the entire seas on their own. Today, we need at least four Yonko who control the seas. That just implies that Rox were Incredibly powerful.
These are Blackbeard aka Teach, Big Mom aka Charlotte Linlin, hundred beasts Kaido and Red-haired Shanks. Before these four Yonko, there were three pirate crews that ruled the seas. These were Gol D. Roger’s, Shiki’s and Whitebeard aka Edward Newgate’s crew. But Rocks was a pirate crew that ruled entire seas all by themselves. This tells us how big this crew would have been and how strong they were. Also, we got to know that this pirate crew disbanded when their captain was defeated by Navy.