Get ready for Zacian, Hero dog! It makes a splash in PvP, with some decent moves, doesn’t quite make the cut for PvE raids.. Just farm them for your dex, and XL for when the shiny with a special move is finally released!
Metagross is top of the hill for this, make sure to make one during the event, or you need to trade for one, they pop up all the time as a top counter. It’s rare to flex your poison types in a raid, but Roserade is one of my favorites and not too hard to find.
Go to the official counters page for a complete list including Shadows and Megas to see how your Pokemon perform.