Crocodile was a Shichibukai of one of the seven pirates who works for the World government hunting pirates, although he was stripped of his title after attempting to take control of the desert kingdom, Arabasta.

Mr. 0 himself

He also has a skill for making flawless plans and seeing things that would escape most others attention and deduce a correct conclusion from nearly no information.

Luffy

Crocodile was once care free and optimistic , it was stated by Crocodile himself that he was not much different from Luffy once, and he also wanted to become the Pirate King and have adventures. As time went by, he grew in power and experience and his once optimistic outlook faded. Crocodile came to let go of his dreams, eventually becoming one of the Shichibukai. At some point, either before he became one of the Shichibukai or after, Crocodile learned of a weapon called Pluton and became very interested in it.

Crocodile secretly started a mysterious group, called Baroque Works.

Zolo

It is known that he found Nico Robin at the age of 24, and made a deal with her. He'll protect her and give her a home, and she can be his partner. In return Robin will read the Poneglyph and find the location of Pluton.

After years of planning, all the Baroque Works agents finally met Sir Crocodile, and were given their final assignments.

Nico Robin

Tashigi, going by her own justice as Captain Smoker ordered, arrested Sir Crocodile, who was stripped of all titles and permissions granted by the Marines and the World Government.

He was taken to a prison with the Baroque Works members ,

Smoker the bounty hunter