Dragonite is a Dragon/Flying type Pokémon, which makes it especially weak against Ice moves, and weak against Rock, Dragon, and Fairy moves. Therefore, the best counters for Dragonite are Pokémon with Ice, Rock, Dragon, or Fairy moves. Here are some of the best options:

• Lapras with Ice Shard/Ice Beam or Ice Shard/Blizzard
• Mamoswine
• Weavile
• Galarian Darmanitan
• Mega Gardevoir
• Shadow Mamoswine

Its important to note that Dragonite is also resistant to Water, Fighting, and Ground moves, which are commonly used by Ice and Rock Pokémon. Therefore, its best to use Pokémon with Dragon or Fairy moves to counter Dragonite. Additionally, Dragonites attacks are mostly Dragon-type, which can only be resisted by Steel or Fairy-type Pokémon. Fairy-type moves are recommended as they will also deal super effective damage.