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The legendary Reshiram has arrived in Pokémon Go, and will appear first in 5-star raids So let's get to know the best counters to defeat him as easily as possible.
Reshiram belongs to the Dragon and Fire types, so it is weak against Dragon, Rock and Ground types. Almost all suitable counters are dragons, but they must have a suitable secondary type. Also, Rock-type counters are quite useful.
At a general level, the ultimate counter is Dialga, with Dragon Breath as a fast attack and Draco Comet for a charged attack. With almost any attack that Reshiram uses, we will have an advantage if we carry one or more Dialga.
It is important to choose high level counters, boosted with stardust and candy, that also have high IV values in Pokémon Go. That's where Dialga can fail, as it hasn't been in raids many times, and maybe we don't have very strong specimens.

Based on this, the 10 best counters for Reshiram at the moment are:
- Dial with Dragon Breath and Dragon Kite.
- Rayquaza with Dragon Tail and Anger.
- Palkia with Dragon Tail and Draco Kite.
- Rampardos with Antiaircraft and Avalanche.
- Haxorus with Dragon Tail and Dragon Claw.
- Salamence with Dragon Tail and Draco Kite.
- Rhyperior with Mud Slap and Rockbreaker (legacy attack).
- Dragonite with Dragon Tail and Draco Kite.
- Terrakion with Anti-Aircraft and Avalanche.
- Tyranitar with Anti-Aircraft and Sharp Rock.
Reshiram is boosted if the weather is sunny or windy inside Pokémon Go. His maximum combat points (CP) are 2,307 CP (i.e. IV 100%) under normal conditions, and 2,884 CPif empowered.
Regarding the players needed for the raids, with 3 or even 2 people it is possible to defeat Reshiram if they have counters raised to the maximum level and take advantage of the bonuses (weather and friendship).
In a more realistic environment, it is recommended about 6 high-level trainers, or about 9 medium level players to successfully face the combat, always depending on the counters used.

Reshiram, the True White Pokémon
Reshiram, the so-called True White Pokémon, was originally discovered in the Unova region (Tesselia in Spanish translation). It belongs to the fifth generation, released in the 2011 Pokémon Black and White games for Nintendo DS.
Reshiram's regional Pokédex number is 149, while the national Pokédex number is 643.
Reshiram is the Pokémon of reality in the mythology of the game, which meets its opposite in Zekrom, the pokemon of imagination. Both creatures were one in the past, and after being divided by an impact as a remainder was left a third legendary called Kyurem (which has black and white versions).
It's official Reshiram, Zekrom, and Kyurem will be coming to 5-star raids in Pokémon Go, but we only know dates for the first one: May 26 to May 16 June.
At first there will be no shiny version (variocolor), but it is to be imagined that it will be obtained in future raids or rewards (weekly field mission or fighting league).
For now It's time to prepare the counters for Reshiram, who, although he is not a very complicated opponent, the restrictions due to the coronavirus epidemic will force many to use Pokémon Go remote raid passes to stay home.