In this episode, Luffy uses his Gear 4 transformation for the first time against Doflamingo. Here's a brief overview of the episode:
"The Boundman Appears! Luffy vs. Doflamingo" Anime Episode Number: 629 Manga Chapter: 700 luffy gear 4 first episode
The transformation takes place during the climactic battle against in the Dressrosa Arc. After seeing his Gear 2 and Gear 3 attacks fail to break Doflamingo’s defenses, Luffy realizes he needs a form that combines speed, power, and durability. How Gear 4 Works: The Science of "Muscle Balloon" In this episode, Luffy uses his Gear 4