Luffy Gear - 4 Episode

Sources: -One Piece Anime (Episodes 746) -One Piece Manga (Volumes 76-79)

And standing in the center was a demon.

"You're finished, Straw Hat! You couldn't even touch me in your little rubber balloon form!" He swung his leg, a rain of razor-sharp "Goshikito" threads slicing toward the crumpled form of Monkey D. Luffy, who lay buried in the rubble of the royal plateau. luffy gear 4 episode

Doflamingo’s smirk vanished. For the first time, his eyes widened behind his sunglasses. "What... are you?"

His arm didn't just swell. It distorted . The bone, the muscle, the very concept of his rubber body screamed as he forced his Haki—the hardened will of the conqueror—into his musculature. It wasn't air he was inflating. It was his resolve . Sources: -One Piece Anime (Episodes 746) -One Piece

Then, the rubble stirred.

Doflamingo didn't get knocked back. He was driven . Driven down like a nail into the bedrock of Dressrosa. The entire island flexed . The royal plateau split in two. A crater a kilometer wide opened up beneath them. Luffy, who lay buried in the rubble of the royal plateau

To understand the impact of the episode, one must first understand the antagonist: Donquixote Doflamingo. Prior to this episode, Doflamingo was established as an insurmountable threat, possessing both a powerful Devil Fruit (Ito Ito no Mi) and mastery of all three forms of Haki.