Triple punching anything makes me a sad panda.
Try this (and hey, if you don't like it, at least you can get another mew.. or just more elemental punch tm's.. or something better like thunderbolt and flamethrower).
Mew @ Leftovers
Swords Dance, Thunder (or Thunderbolt), Earthquake, Softboiled.
~ Softboiled fills in for Mew's inability to learn recover (in GSC anyway, not sure if thats changed in third generation), Swords Dance + Physical Move is a wrecking ball, and thunder (thunderbolt if you chose it) basically means the only thing able to take limited damage from your moves is Gligar (which sucks anyway so who cares). Amazing Set for Stadium/link in my experience.