Waluigi was born at an unknown time but was taken in by Wario before Mario Tennis 64. Since then they have been together everywhere besides in the Smash Brothers series nor any mainline Mario games. At his debut, he instantly gained a rivalry with Luigi and a crush on Daisy. Most of his traits and personality were inspired by Wario meaning that Waluigi had known Wario for a very long time. Due to his appearance, Waluigi was likely a name given by Wario combining his own name with Luigi's. And according to Nintendo on Wario's Warehouse, Waluigi was tortured by Wario on a rack to increase his height, to make him the superior Luigi.
Powers & Abilities
Mastery of Sports: Like most Mario characters Waluigi is really good at sports, including tennis, go kart racing, soccer, baseball, hockey, basketball, etc.
Able to swim through the air
Able to flash his eyes red: As shown in Mario Tennis, his eyes would flash red whenever he'd win a round
Ability to spin fast enough to drill at least 500m into the Earth in a half hour, and also survive the magma (Wario's Warehouse)
Tennis Racket: A tennis racket is the weapon Waluigi uses most often. He is most known for using it in Super Smash Brothers Brawl as an assist trophy.
Bob-Bombs: One of Waluigi's most used weapons is bombs his special ability in Mario Kart Double Dash is to throw bombs.
Able to destroy solid walls by throwing a baseball at them.
Destroyed a Thwomp by jumping on it. (Mario Party)
Can destroy boulders by hitting them many times. (Mario Party)
Knocked out Bowser with sheer force
Outran a giant boulder. (Mario Party 6)
Escaped the gravitation of a mini black hole. (Mario Party 6)
Fell from an airship and hit the surface and survived.
Survived an explosion the size of a castle. (Mario Golf)
Considered a Skill type in the Mario & Sonic Olympics series.
Is one of the best archers in Mario & Sonic Olympics.
He can jump as high as Luigi
Overshadowed by Luigi. (This is quite unfortunate, as Waluigi is superior.)
Despite being popular among fans he rarely appears in the main series Mario games.
It can be easily tricked and manipulated.
He's very selfish and only cares about himself and wario/daisy.