i feel adrien in going to be my easiest gym.
mega mawile->flare blitz ohko
klefki->earth power/Flare blitz ohko
gardevoir/Mr mime/sylveon->iron Head/Heavy slam ohko
Whimsicot->sludge wave ohko
Any other fairy that he possibly could have cant do a scratch to a steel or poison.I feel that at this point fairy pokemon are very easy to counter given the amount of steel and poison pokemon (that we have)that have access at these moves(flash cannon,iron head,heavy slam,gyro ball,iron tail,meteor mash,sludge wave,sludge bomb,gunk shot,poison jab etc.)
I think the fairy gym could be more challenging if we would have faced them earlier