What is the music playing in One Piece episode 644 when Hajrudin encounters Lucy aka Luffy? What is the music playing in One Piece episode 644 when Hajrudin encounters Lucy aka Luffy?
The song which starts playing at 22:00 and continuing on to the scene where Lucy/Luffy stands back up and faces Hajrudin is ルフィ猛攻! (Luffy's Fierce Attack!) from the album ONE PIECE THE MOVIE Norowareta Seiken Soundtrack.

The song can be sampled on Amazon and YouTube.