Quoted By:
I'm telling you, the best thing to do with Flareon is run him as a specially defensive mixed attacker.
Assault vest
252 sp. Def, 252 speed, 4 hp
Gentle Nature(+sp. Def, -def)
Quick Attack
Iron Tail
Scorching Sands
Mystical Fire
The idea is that you as the trainer have to find a way to make sure Flareon never gets hit with physical attacks. If you get hit with physical attacks, you die. If you're up against a special attacker, honestly after a single Mystical Fire fucking nothing is able to hurt you, even super effective STAB attacks honestly do fuck all to Flareon running this set as long as they are special attacks. Remember, anything that has any potential to physically hit Flareon is an auto lose, but if you can avoid that, it's actually a tanky mixed attacker with enough speed to at least reliable out speed any tanks. It hardwalls Togetic, Gardevoir, and a lot of other fairies and kills them with Iron Tail. Scorching Sands is basically just for coverage and burning people, and quick attack is to give you the potential to revenge kill. Flare Blitz is a meme, you're too slow and even under the best of circumstances Flareon basically kills himself by doing it.
I've tested a lot of bullshit with this pokemon, this is the most successful thing I've settled into.