Snake, in my opinion is overpowered, because two hits from his normal attack launches you, and then by the time you've gotten back up, he's hitting you again. This can be countered by someone like Link or Lucas, with long range attacks.His Final Smash is ridiculously powerful, so you need Fox or Sonic to dodge, preferably Sonic because he can jump better. Anywaaaay...
Jiggly Puff and Ike. Jiggly Puff because there is this glitch, and ike cause he's powerful and has an awsome final smash. (see "Jiggly Puff Glitch" for more info on the glitch)