Admiral Kizaru was set up to be a significant antagonist for One Piece's Egghead Arc. Besides being one of the Navy's highest-ranking officers, he was someone the Straw Hat Pirates were badly beaten by on a previous leg of their journey. Many fans assumed his overwhelming presence in the story would lead him to be the final antagonist of the arc. Thus when Monkey D. Luffy squared off against him in Chapter 1091, "Sentomaru," everyone was in it for the long haul. This would be the fight that would show whether Luffy was as strong as the papers made him out to be or if he still had a little ways to go to truly earn his Emperor status.
Source：https://www.cbr.com/one-piece-luffy-vs-kizaru-end-result/
