Magellan

Magellan ate the Doku Doku no Mi, which lets him produce and control poison. His poison threatens opponents through direct contact and gas, making an ordinary close-range attack dangerous even when it lands.14

His techniques include Hydra, a large poison attack, and Venom Road, which he uses during the pursuit of Luffy. These powers let him control the space around an opponent and make retreat through Impel Down's corridors difficult.45

The later Venom Demon technique raises the threat further: its poison spreads through surfaces, and Mr. 3's wax protection no longer provides a lasting defence. The prisoners have to escape the advancing poison.6

For the fruit's role in the prison battles, see Magellan's Devil Fruit.

Luffy does not defeat Magellan in their first fight. Magellan overwhelms him with poison in chapter 535 and orders him taken to Level 5. Luffy's attempt to push through the warden leaves him incapacitated.2

Their later encounter ends in an escape rather than a decisive victory over Magellan. In chapter 547, Luffy and Mr. 3 combine a Gear Third attack with a giant wax wall to push the advancing poison back briefly. The wall is being eaten away, so the opening buys time rather than ending the threat.7

This distinction matters when reading about Luffy's fight with Magellan: forcing him back during a retreat is different from defeating him.

The escape depends on several allies acting together. Luffy and Mr. 3 delay the poison, Ivankov propels the fugitives away from the entrance, and the whale sharks called by Jinbe carry them across the water toward the captured ship.7

Magellan remains the immediate danger throughout this sequence. The group survives by creating enough distance to leave the prison, rather than by removing him from the fight. See the Impel Down escape explained for the linked sequence.

Magellan was chief warden during the Impel Down breakout. Chapter 581 reports that he was badly injured in its aftermath and receiving intensive care. The cover of chapter 665 later identifies him as vice-chief warden, distinguishing his later rank from his position during Luffy's rescue attempt.83

For the role during that arc, see who was the warden of Impel Down. The older title explains his authority in the prison battles; it should not be confused with his later appointment.