From my personal experience Wario is at its fullest when paired with any character that is very offensive so that Wario can camp and support with his lovely Uairs Dairs and Wafts, so GnW and (from my personal exp again) a semi-aggresive Snake and maybe even MK are among the best partners.
I once played doubles with Aziel (probably one of the best Snakes in Mexico) and his Snake and my Wario won like 10 straight matches with other friends who also play VERY competitively.
P.S: Wario + Wario = Chuck Norris Incarnate! and also when there is only 1 opponent I LOOOOOVE doing BITE LOCK! we just grab the character with a bite and the other Wario stays in front (and REALLY close so we don't have to jump) of them to catch'em again with the Bite, it's hilarious!
I once played doubles with Aziel (probably one of the best Snakes in Mexico) and his Snake and my Wario won like 10 straight matches with other friends who also play VERY competitively.
P.S: Wario + Wario = Chuck Norris Incarnate! and also when there is only 1 opponent I LOOOOOVE doing BITE LOCK! we just grab the character with a bite and the other Wario stays in front (and REALLY close so we don't have to jump) of them to catch'em again with the Bite, it's hilarious!