>>56365573If you mean the Wild Pokémon we usually go up against in Wild Battles, those ones are probably fine after Fainting and recover easily after a while. Remember that Pokémon Battles are different thing from a literal fight and don't result in death.
The Wild Pokémon we don't see... Yeah... Those likely are suffering far worse than simply Fainting, as a result of other Pokémon. Those Wild Pokémon typically fight each other to the death and hunt each other.