I don't think Walking Wake has any real counterplay in a meta where we have no Dragon Resist and it has 120 BP Water Coverage to hit all the ones that do resist, esp w/ Proto boosting its damage output. I was thinking Utility Umbrella Tera-Fairy Slowking could be a counter, but that is a shitty meme that I am 100% sure it won't work. If Walking Wake runs Hydro, it still retains full power vs Tera Fairy Slowking, so it will 2HKO anyways lol.
252 SpA Choice Specs Protosynthesis Kingdra Draco Meteor vs. 252 HP / 252+ SpD Slowking: 271-321 (68.7 - 81.4%) -- guaranteed 2HKO
252 SpA Choice Specs Protosynthesis Kingdra Hydro Pump vs. 252 HP / 252+ SpD Slowking: 114-135 (28.9 - 34.2%) -- 4% chance to 3HKO
252 SpA Choice Specs Protosynthesis Kingdra Hydro Pump vs. 252 HP / 252+ SpD Tera Fairy Slowking: 229-271 (58.1 - 68.7%) -- guaranteed 2HKO
Boots Slowking is still an okay check I think and can force it into a position where it will either need to Tera or reset sun, but still not ideal. Another solution is running Snowscape on random Pokemon to lower its damage / speed or using Blissey on every team, but that seems kinda like a not good dynamic.
252 SpA Choice Specs Protosynthesis Kingdra Draco Meteor vs. 252 HP / 252+ SpD Slowking: 271-321 (68.7 - 81.4%) -- guaranteed 2HKO
252 SpA Choice Specs Protosynthesis Kingdra Hydro Pump vs. 252 HP / 252+ SpD Slowking: 114-135 (28.9 - 34.2%) -- 4% chance to 3HKO
252 SpA Choice Specs Protosynthesis Kingdra Hydro Pump vs. 252 HP / 252+ SpD Tera Fairy Slowking: 229-271 (58.1 - 68.7%) -- guaranteed 2HKO
Boots Slowking is still an okay check I think and can force it into a position where it will either need to Tera or reset sun, but still not ideal. Another solution is running Snowscape on random Pokemon to lower its damage / speed or using Blissey on every team, but that seems kinda like a not good dynamic.