Finally, in February of 2020, Nintendo cut ties with a game publication after one if its reviewers leaked images of Sword and Shield. Later on, The Pokémon Company began a lawsuit against the leakers.
The lawyers said the leaks caused The Pokémon Company "irreparable injury" in their ability to market the game. Shortly after release, lawyers for The Pokémon Company began searching for the Sword and Shield leakers. We already knew that select Pokémon from previous generations would not return to Sword and Shield, but these leaks further fueled the fire of the "Dexit" outrage and backlash on social media. A list of Sword and Shield leaks detailed the Galar region Pokédex, Gigantamax forms, Galarian forms, and more. Then, the firestorm started in early November 2019, just before the games were set to come out. Months before release, a leak surfaced that ended up containing many true elements of the final games, including Team Yell, the rival's names, regional evolutions, and more. The most well-known example is 2019's Pokémon Sword and Shield, which suffered from a handful of leaks leading up to release, followed by a lengthy legal pursuit.
Even further back, Pokémon games have had the tendency to leak, both leading up to their release and their announcements.