Answer: Wario
When Nintendo was searching for a name for the character that would become Mario’s dark doppelganger, they didn’t have to look far. By combining the word Mario with the Japanese word for bad, “Warui”, they came up with Wario. Even better, the W in English looks like an inversion of the M in Mario.
When it became time to cook up an evil copy of Mario’s brother Luigi, they used the same naming convention: Luigi became Waluigi—sadly, not quite as catchy and visually appealing a name as Wario.
In addition to his appearances in Mario-centric games and broader games like those in the Super Smash Bros. fighting game series, Wario has over a dozen titles devoted just to his character like Wario Land, Wario Land: Shake It!, and Wario’s Woods.