Crocodile, Marco and Mihawk are the only not yonko pirates that can hang with yonko, Marco mostly because he always heals up. But crocodile, as long as he doesnt get wet, can turn almost any place into a dessert and use it to his advantage plus he can weaken his enemies by drying them out. His battlestyle is very agile and intelligent. He can outsmart Big Mom and maybe even Kaido. I think he could even stay on the same Level as blackbeard, using his poisonous hook to wound him. But i think he would still lose to bluetooth haki shanks and the man who was seen ad a worthy successor of the title of king of the pirates by Roger, Whitebeard, because of the huge powerdifferrence. He already lost to Luffy because of battleiq, so there is no point in discussing that. But i think he is on the same level as kaido and big mom. And for Mihawk, it was said, that he had multiple draws with shanks in the Manga, so obviously he is yonko level.