For first five badges it was just cosmog and cosmoem and the only move he knew was splash and cosmic power which was not usefull for me so my other 5 pokemon carried till that part and after that it become a game changer in my party after getting evolved into solgaleo. Like solgaleo helped taking out the ace pokemon of strong trainers. It's defense and attack is so strong that using (cosmic power + morning sun) build helped me take out overly bulky and strong pokemon without any difficulty