Trainers who want to solo Tentacruel Battle Raids in Pokemon GO should use this counter strategy.
Pokemon GO trainers must master the ability to defeat three-star Battle Raids. Soloing these battle raids is often possible for experienced players who have done their research, which speeds up the process by eliminating the need to wait for groups and, in some cases, results in more Premier Balls as encounter rewards.

To successfully solo a three-star Battle Raid, Pokemon GO trainers must identify the boss’s weaknesses and assemble a team capable of exploiting them. In order to defeat a Water/Poison dual-type Pokémon like Tentacruel, the best Electric, Ground, and Psychic-type Pokémon are required.
Those who adhere to this strategy and invest the time and resources necessary to optimize their roster should be able to defeat Tentacruel on their own. Remember that getting the perfect movesets in place is very effective, so don’t be afraid to use up Elite TMs if necessary. However, players who aren’t as confident (or who are at a lower level) should be able to win with just one or two allies if they enter the battle together.

Tentacruel Weaknesses
Tentacruel, the Water- and Poison-type boss of the Battle Raid, is vulnerable to Electric-, Ground-, and Psychic-type attacks.
Best Tentacruel Counters Alakazam (Mega)
Psycho Cut/Psychic
Latios (Mega) – Zen Headbutt/Psychic
Zen Headbutt/Psychic – Latias (Mega)
Thunder Fang/Wild Charge is a Manectric (Mega) ability.
Charge Beam/Zap Cannon. Ampharos (Mega).
Mewtwo – Confusion/Psychic Attack
Gengar (Mega) – Shadow Claw/Psychic
Slowbro (Mega) – Bewilderment/ Psychic
Hoopa (Unbound) – Bewilderment/Psychic
Xurkitree – Spark/Discharge
Zekrom – Charge Beam/Wild Charge
Metagross – Zen Headbutt/Psychic
Confined Hoopa – Confusion/Psychic
Thundurus (Therian) – Volt Switch/Thunderbolt
Landorus (Therian) – Earthquake/Extrasensory
Trainers who adhere to these counters should have no trouble speeding through this Battle Raid on their own. Three-star Battle Raids may not be as exciting as Legendary and Mega Battle Raids, but they still offer rewards that can be difficult to pass up if players have extra Raid Passes and an interesting one appears at a nearby Gym. Even at the three-star level, Battle Raids are a reliable way to earn a great deal of Candies, valuable items, and decent experience.
Check back soon for a plethora of additional Pokemon GO strategy guides, news, and updates. Trainers, until then, best of luck out there!