>>53333531>Never need to trade anyone if you do the raidsThere are two exceptions: The Cover Legendary and the Paradox Pokemon.
Recent games usually give you a second cover legendary, so it's easy to trade your extra for someone else's. As for the Paradox Pokemon, there's a new feature added this generation that lets you link up and play with another player online. When you're doing it, you'll see spawns from their game even if they're version exclusive. And all seven Paradox Pokemon spawn in the same place, so you can grab them within a few minutes.