6. Marco the Phoenix
Marco the Phoenix is the former first division commander of the Whitebeard Pirates. He is a user of a powerful mythical zoan type devil fruit which allows him to transform into a phoenix. He can produce blue flames which are capable of healing almost any wound suffered by him and now we know that he can cure others as well with this ability. He went head to head against multiple Admirals in Marineford war and survived quite gracefully.
Blackbeard is the newly crowned Yonko after the time skip. He is the only known user of more than one devil fruit. He has the power of Gura Gura no Mi devil fruit which he acquired after the death of Whitebeard. With its hell, he can cause earthquakes out of absolutely thin air. He also has another devil fruit ability known as Yami Yami no Mi which reduces everything to nothingness. He is easily one of the strongest pirates alive and thus is even stronger than Admirals.