Dick

Dick the Mountain Whale was a bandit in the East Blue who fought with a bazooka (although it looks like a bazooka-sized Derringer pistol) and was the brother of Billy. He had a bounty of 10,000,000.

History
After hearing his brother Billy had been taken out by a bounty hunter, he went looking to finish whomever was behind his brother defeat. While pillaging a village, he defeated a boy named Harry who tried to save his village's supply of food. He fought Johnny and Yosaku and easily defeated them under the belief that they were the ones responsible for turning in his brother, however they were lying.

Eventually Zoro turns up and confirms he was the one who had defeated his brother. Zoro beat Dick to claim his bounty to buy two new swords after he broke his old pair in a previous fight.

Trivia

 * "Mountain whale" (山鯨) is an old word for wild boar.