Luffy vs Arlong

In the anime, Arlong attacks Luffy using his fish-man abilities, including "Shark on Darts". Luffy punches Arlong in the face, destroying his teeth. Arlong reveals that he can regrow his teeth, and each new set is stronger than the last. Luffy takes one of Arlong's teeth and uses it as a weapon.
Arlong is the first major threat Luffy has to face, and their fight is intense. Arlong bites and cuts Luffy with his sharp teeth and nose.