There is one activity is all of the recent (main version series) Pokémon games that I’ve never successfully done. The Battle Tower. It was introduced in the second generation of Pokémon games, in the Crystal version game, and has been a part of every game since. In some of the games, the name of the activity changed, but it was still largely the same thing. There have been changes over the years as the meta of Pokémon has shifted and evolved, but I only know this stuff because I looked it up to write this post. I’ve never actually participated.