Clefairy is a normal type which means that he’s a very well rounded pokemon. Most attacks won’t be that effective against him and you never know what attack he’ll throw out next. Still, that’s never fazed Pikachu in the past and it won’t be stopping him this time. Pikachu is far too quick to get hit so easily and one good Volt Tackle will end this thanks to Pikachu’s intense power. Pikachu wins.