Marco was the former first Division Commander, and captain of the Whitebeard Pirates, after Whitebeard’s death. During the battle of Marineford, Marco was one of two people who fought toe to toe against Kizaru.
Marco can also use Armament, and Observational Haki. He also possesses a Mythical Zoan type of Devil Fruit which allows him to turn into a Phoenix and with which he is able to heal from any damage. If Marco and Admiral Kizaru fought again, Marco might be able to defeat him and also it would be a fight to remember.