Great Wario lives up to its name now, but this wasn't always the case, as it used to be a spriteswap of Big Eli King's self character; fortunately with the help of @ndroide, it was fixed, making a solid and famous character in the process.
Wario is a slow, four-button character, though his gameplay style is nothing too fancy. Some of his moves makes him temporarily invincible and can be useful against characters with brutal A.I.
Being a King of Fighters-styled character, Wario has only a few combos, but to make up for it, they are very high-damaging. You can use Wario's kart to trip its foe and use its 3-hit combo system and follow it up with ether its Wariopunch or Crokofire (or both if you have enough Power).