The more Eevee loves its Trainer, the greater the move’s power. It never misses.
Veevee Volley is the move that utilises the Happiness in a more positive light, by rewarding the amount the Pokémon likes the trainer. It is a Normal Type Physical Attack with 20PP and 100% accuracy. Its power is calculated by the following means:
Base Power = Pokémon Happiness / 2.5
This gives a maximum result of 102 and a minimum result of 1