top 5 who were both pirates and marines in one piece

#5 Koby

Koby is a Marine Captain who trained together with Helmeppo under Vice Admiral Garp’s supervision. He is currently a member of the Marine special forces unit SWORD. He was formerly an involuntary cabin boy for the Alvida Pirates until he was liberated by Luffy.

#4 Vergo

Vergo was one of the four elite officers. At age 26, he enlisted in the Marines under Doflamingo’s orders. Having spent 15 years ascending the ranks, he nevertheless was an enemy to the organization from the beginning, as he assisted Doflamingo in criminal activities by abusing the privileges as a high-ranking Marine officer, as well as passing off vital information and coverups. He was dishonorably discharged when Smoker reported him to Sakazuki

#3 Ceasar Clown

Caesar Clown used to work with Marines as their scientist. During the Dressrosa Arc, Donquixote Doflamingo declared Caesar to be his direct subordinate, meaning Caesar was a de facto member of the Donquixote Pirates. He also took part in a rebellion against Big Mom together with Fire Tank Pirates and Straw Hats.

#2 Donquixote Rosinante

Donquixote Rosinante was the younger brother of Donquixote Doflamingo. He became an Elite Officer of the Donquixote Pirates, serving under Doflamingo under the codename Corazon.
The truth, however, was that he was a Marine Commander, working undercover in order to stop Doflamingo. He was found out by the former Corazon, Vergo, and was executed by Doflamingo 13 years ago.

#1 Kuzan

Kuzan, better known by his epithet Aokiji, is a former Marine Admiral and the first one to be revealed. He was nominated by Sengoku for the position of Fleet Admiral. However, after losing the position to Sakazuki, he resigned from the Marines and affiliated himself with the Blackbeard Pirates. It is unknown what standing he has with the crew, but some like Jesus Burgess are not so quick to trust him because of his past as a Marine, but Blackbeard pays it no mind.