(Wario = Mario's "alter ego"?!?).
Mario is mild-mannered - Wario is rude
Mario is handsome and fit - Wario is ugly and fat
Mario is selfless - Wario is greedy
Mario's name starts with M - Wario's name starts with an upside-down M
Mario is hygienic - Wario is not hygienic
How many more examples do you need? I'm pretty sure Wario was originally created to be an opposite version of Mario.