As commander of the first division of the Whitebeard Pirates, Marco has authority over the lower-ranking subordinates. In addition, he is also one of the top four commanders of the Whitebeard Pirates, making him one of the top four fighters on board under Whitebeard himself.
He is capable of retaining consciousness despite the powerful Haki of Shanks, a Yonkou. He has incredible reflexes, as he is able to instantly respond to Kizaru's light-speed movement and attacks to protect Whitebeard. He was also able to touch Kizaru, who is normally intangible due to his Logia ability. This may indicate that Marco is capable of using Haki.
Marco possesses super-human strength, as shown when he kicked Kizaru down to the ground at extreme speed, however it is unclear if it's natural or comes from the fact that he is a zoan-user.
Marco ate a Devil Fruit referred to as a Mythical Zoan that turns him into a Phoenix. This first and foremost gives Marco increased speed and flight, as well as the possibility of launching aerial attacks. Along with being able to transform into a blue phoenix, the fruit allows him to regenerate any wounds with fire. It is a power that is said to be even rarer than Logia. The fruit gave him his nickname: Marco the Phoenix. Marco has more control over his Devil Fruit than any other Zoan-user to date; it's so great that he can change just some limbs while the rest of the body remains human.
(Source: One Piece Wikia)
