Overview

After beating your Mewtwo, look for the following CP values. These values are those of a Mewtwo with perfect IV's.
  • REGULAR: 2275
  • WEATHER: 2844

​Although it's stats are modified, it still packs quite a punch. It has 300 attack, 182 defense, 193 stamina. As a Raid Boss, it has a CP of 49340.

Mewtwo is a Psychic-type. It has access to the following moves:
  • FAST MOVES: Confusion, Psycho Cut
  • CHARGED MOVES: Hyper Beam, Shadow Ball, Psychic, Focus Blast

COUNTERS

Gyarados

Gyarados is the best counter to Mewtwo. It attacks quickly with super-effective moves. It also resists the dreaded Focus Blast.

​Here are the moves you'll want:
  • FAST MOVE: Bite
  • CHARGED MOVE: Crunch

Scizor

Scizor is your second-best option. It attacks and charges its attack bar incredibly quickly.

​Here are the moves you'll want:
  • FAST MOVE: Fury Cutter
  • CHARGED MOVE: X-Scissor

mewtwo

If you already have a Mewtwo, you can put it to good use against the Raid Boss. Be careful, because if your Mewtwo can have Shadow Ball, so can the Raid Boss.

​Here are the moves you'll want:
  • FAST MOVE: Psycho Cut
  • CHARGED MOVE: Shadow Ball

houndoom,  Umbreon

Houndoom and Umbreon are some of your best Dark-type options. While not as offensively strong as Gyarados, it does not have a double weakness to the Fighting-type Focus Blast like Tyranitar.

​Here are the moves you'll want:
  • FAST MOVE: Snarl
  • CHARGED MOVE: Foul Play

Tyranitar

Tyranitar is the best Dark-type Pokémon. However, it is four-times weak to Focus Blast. If Tyranitar isn't recommended to you, do not use it.

​Here are the moves you'll want:
  • FAST MOVE: Bite
  • CHARGED MOVE: Crunch

Dragonite

As with many Raids, Dragonite is a great choice. It is a great generalist, and deals a lot of damage.

​Here are the moves you'll want:
  • FAST MOVE: Dragon Tail
  • CHARGED MOVE: Outrage

Other  viable  counters

If you want to deal a lot of damage, glass-cannons like Sharpedo, Banette, and Absol can be useful.

Alakazam and Gardevoir can also be put to good use with Shadow Ball.

Pinsir can also be useful. Aside from Scizor, it's your best choice for Bug-type attacks.

Heracross and Gengar can also be used. While Heracross' Bug-type and Gengar's Ghost-type are super-effective, their Fighting-type and Poison-type makes them weak to Psychic attacks.
IMAGE CEDIT: The Pokémon Company