Makes me wonder how a vaporeon even faints.
I guess if they pick up enough speed and slam into something hard enough they'll be knocked out for a bit, but if they can basically vaporise (get it) their entire body and turn back, vaporeon is technically unkillable.
Although I guess you could defeat it by trapping it in a sponge or something.
Which is why it's logically most compatible for fighting other pokemon.