Raikou is an Electric-type Legendary Pokémon and is only weak against Ground-type attacks. Being a single-type Pokémon, Raikou has only one weakness, and it can easily defeat an unprepared trainer. Therefore, the best way to defeat Raikou is to use your strongest Ground-type Pokémon. Here are some of the best counters for Raikou:

• Flygon
• Groudon
• Rhyperior
• Torterra
• Mamoswine
• Excadrill
• Garchomp
• Landorus (Therian)
• Shadow Garchomp with Mud Shot and Earth Power
• Excadrill with Mud-Slap and Drill Run
• Primal Groudon with Mud Shot

It is important to note that Raikou is considered one of the most dangerous Raid bosses in Pokémon Go. Therefore, it is recommended to team up with other trainers to ensure you defeat it.