At the beginning of the battle, the fast move of the active Golduck is Confusion. To beat the Flareon easily, the player switches the Golduck to the another one which can use Water Gun.
2. Water Gun vs Ember
The Golduck uses Water Gun, and the water-type fast move is super effective against the Flareon. The Flareon uses Ember, but the move is not effective to the attacker conversely.
3. Flareon's Flamethrower
The Flareon uses Flamethrower, the fire-type charge move, but the move is not effective against a water-type Pokemon. The Goludck's Water Gun damages the Flareon much. and the defender is finally beaten down.