Waluigi is that one person that almost everyone can agree is boastful. Heck, the only person who doesn’t think of him that way is his partner, Wario! Being a mean spirited troublemaker, Waluigi is brash, selfish, and takes great pride in his antagonistic schemes before he even executes them(And they never even work). He rarely cares about anything other than Wario, who seems to be his only friend, and Princess Daisy, the one he deems will be his girlfriend one day. Daisy has no interest in him whatsoever, and is instead on his "self-proclaimed" rival, Luigi. With bad luck after bad luck, Waluigi has a great amount of self-pity due to feeling that nothing good ever happens to him, and always blames his misdeeds on everyone but himself, and it doesn't help that he never gets any spotlight and is quite forgotten about by many people. In fact, Luigi doesn't even KNOW Waluigi doesn't like him that much. Poor guy...

For his voice, take references from Charles Martinet's voice of him.