it matters: the level, the stats, the stats for the pokeathlon dome and the attacks it knows like arceus.
machamp
Fighting type Pokemon
I would suggest fighting the elite four with a water, fire, ice, rock, electric, and fighting type pokemon.
Snorlax is a normal type Pokemon. Therefore, a Fighting type pokemon using Fighting type moves will be super effective.
A dark than fighting.
Fighting type moves are best
Statistically Meloetta is the best fighting type, but Meloetta is mixed type. The best pure fighting type is Mienshao statistically. My personal favourite is Primape
some Pokemon you might want are Cobalion, (steel-fighting) Terrakion (rock-fighting), and Virizion (grass-fighting). these are legandaries, they help A LOT!
Arceus has the best overall stats. Spiritomb has no weaknesses. It really depends on who you're fighting.
If you mean fighting type, the best you can get is Machamp. However, it is hard to get because you need someone to trade and trade back a machoke, so HItmonlee (You get it at the Fighting dojo) is the best next option. Primeape works too. Avoid Hitmonchan.
depends what your fighting, if ground use flying, if electric use fighting, if fighting use fighting
By Strategy, if you mean best team of Pokemon, i recommend a solid team with a Dark,Psychic,Dragon,Water,Fire, and a Fighting Pokemon.