Poliwrath and Keldeo. But since Keldeo hasn't even been released in games yet, use Poliwrath.
Poliwrath is a water and fighting type.
Keldeo is a Water and Fighting type pokemon.
fighting type pokemons weakness are psychic and flying moves steel is weak aageinst water fire fighting and ground
Rock type Pokemon are weak against Water, Steel, Grass and Fighting.
Rock-type Pokemon are weak against Water, Ground, Steel, Fighting and Grass-type attacks.
Poliwrath is a water and fighting type.
Keldeo is a Water and Fighting type pokemon.
A fighting type, a ghost type, a rock type, a ice type, a water type.
fighting type pokemons weakness are psychic and flying moves steel is weak aageinst water fire fighting and ground
Rock type Pokemon are weak against Water, Steel, Grass and Fighting.
I would suggest fighting the elite four with a water, fire, ice, rock, electric, and fighting type pokemon.
Rock-type Pokemon are weak against Water, Ground, Steel, Fighting and Grass-type attacks.
A Geodude and a Nosepass. You should be fine with a fighting type, a water type, or a grass type.
Water/Ice type pokemon are weak against rock, electric, fighting, and grass type moves
Flying and Psychic do 2x damage to Fighting-type Pokemon.
A fighting type, Ghost type, Fire type, Rock type, Dragon type, Ice type, Water type.
Any fighting, water or grass type Pokemon even ice