Vicious was the leader of a crime syndicate in Cowboy Bebop. He had an old rivalry with the main protagonist over a woman named Julia. He used a katana in battle and had a pet bird that helped him out.
The rivalry between Vicious and Spike is one of the main plot points in the series. No matter how much Spike tries to escape his past, Vicious and he always seem to cross paths until their inevitable battle at the very end that puts both of them to their very best. For somebody who only uses a sword Vicious does pretty well in battle against Spike who uses a gun. Typically guns will defeat swords including in anime, but Vicious shows he is quite the master with his weapon of choice.