One Piece: I'm a Refined Gentleman by Nature, I Just Have a Taste for Killing

Luffy, let me teach you how to kill. How can you be a good pirate if you don't know how to kill? Killing is actually very simple. Once you've done it the first time, there'll be a second, and after that, countless more. Come on, Luffy. Let me show you. Just strike down from here, and you'll kill him easily. What? You say you don't want to kill anyone? How can you become the Pirate King if you don't want to kill? How can you protect your friends if you don't want to kill? How can you stop tragedies from happening if you don't want to kill? Fine. If you really don't want to kill anyone, I'll just kill them all for you.