Ryoma Hoshi, known as the Ultimate Tennis Pro was at the top of his game, he took down a whole mafia by himself using his steal tennis balls. He is tough and cynical person, his past experiences put adults to shame despite his size, he sees himself as a killer, a person the others would not want to get close too. English dub voice preferred, but any deep voice is great, in fact, the  deeper the better (don't take that out of context).