Kaidou is shocked and upset for CP0 boss' appearance, but he can't stop. In that moment, Kaidou remembers when he hit Oden 20 years ago (these memories are from Kaidou's point of view). Oden and Luffy faces are practically the same.
In an AMAZING final double page (for me, one of the best in all One Piece) Kaidou brutally hits Luffy with his kanabo using Color of the Supreme King Haki. “Hourai Hakke” hits Luffy's body directly (Kaidou's kanabo hits Luffy's body like a mallet). Luffy can't defend himself thanks to CP0 boss distraction. CP0 boss manages to move away just in time, so the blow did not hit him.
Kaidou's expression after hitting Luffy is heartbreaking, he is completely shocked. Luffy is badly injured and bleeding a lot. Chapter ends with this sentence from series' editor.
“Emotions are mixed...”