Rayquaza is dragon and flying type. So it has a double weakness to ice types! If you don't have enough of those, then dragon types as usual. In this case, fighting trumps ground against Dialga. The list of top DO@20 counters against Rayquaza is:

Mamoswine: Powder Snow / Avalanche Mewtwo: Psycho Cut / Ice Beam Regice: Frost Breath / Blizzard Weavile: Ice Shard / Avalanche Mew: Frost Breath / Blizzard Walrein: Frost Breath / Blizzard Lapras: Frost Breath / Blizzard Dialga: Dragon Breath / Draco Meteor Articuno: Frost Breath / Blizzard Piloswine: Powder Snow / Avalanche

Weather

So there are lots of non-ice types, but they have ice moves. Make sure to change your moves to ice types.When it is partly cloudy , rock is boosted. Tyranitar(#4), Rhyperior (#7), and Ramparados (#9) are useful then with rock moves.

When it is windy, dragon is boosted. Dialga(#3) and Palkia (#5) rank higher now with dragon moves.

For other weather, there are only minor changes.

Move set

When Rayquaza has outrage, the weaker pokemon faint a little faster and drop in rankings. Consider these tank-ier alternatives Articuno (#2) and Alolan Sandslash (#5) with ice moves.

Comments

If you have any comments or suggestions, please visit this Reddit thread