After Wishiwashi any totem pokemon can be killed turn 1 by just using a super effective z-move before they can act. Kahunas only use z-moves on their very obvious signature pokemon (the one in the same evolutionary family as they're with in the overworld) meaning you can just use your own z-move to one-shot the opponent's z-move user before they can use z-moves. Literally everything game freak tried to do to make the game more difficult is undone by these broken crystals, there has never been a pokemon game where I've had so few of my party pokemon faint throughout the game as Sun.