>>44836915Well if you go by canon, pokemon have a natural fighting instinct, but don't really fight to kill so it wouldn't really be anything like dog or cock fighting, but more like amateur boxing with at low levels, MMA at mid levels, and would really only be potentially lethal at high levels.
That being said, I would probably just be a breeder. There will always be a market for rare or niche pokemon and also Eevees. Eevees would be the perfect pokemon afterall. Give it an everstone collar and it will be a cute little pet forever or evolve it if you want to battle.