MewTwo

Mewtwo is an artificial Pokémon. It is a bipedal, humanoid Pokémon with some feline features. Its body is primarily gray with a long, purple tail and a purple underbelly. On top of its head are two short, blunt horns, and it has purple eyes. A tube extends from the back of its skull to the top of its spine, bypassing its neck. It has a defined chest and shoulders, which resemble a breastplate. The three digits on each hand and foot have spherical tips. Its tail is thick at the base but thins before ending in a small bulb.

According to journals found in Kanto's Pokémon Mansion, after discovering the Mythical Pokémon Mew and gathering some of its DNA, Mr. Fuji used it in his mansion to create Mewtwo, a modified clone of Mew with the goal to making it the most powerful Pokémon of all. It was held and studied in the mansion where horrific gene-splicing experiments were made making the Pokémon vicious and extremely powerful. It eventually broke free and fled the Mansion, destroying it in the process. It is widely known as one of the most powerful Pokémon in existence and is said to have the most savage heart among all Pokémon, lacking compassion and striking fear into its enemy with cold, glowing eyes. Mewtwo conserves energy by remaining motionless in order to unleash its full power in battle. Because it was engineered to be the ultimate opponent in battle, it can only think of defeating its foes. Though rarely seen in the wild, it is said to be resting in a dark cave somewhere.

In Mewtwo Strikes Back, a Mewtwo exemplified its vicious characteristics. It was shown to be capable of levitation, telepathy, mind control, memory erasure, teleporting others to another location, and the creation of powerful storms. However, it was later shown to be caring, protective, and even altruistic. Another Mewtwo in Genesect and the Legend Awakened also shared its aversion to contact with others but was much less belligerent. As shown in POKÉMON Detective Pikachu, Mewtwo can also transfer a human's soul into a Pokémon's body, causing this person to gain control of the Pokémon's body and abilities. It possesses a rivalry with Mew. As seen in Genesect and the Legend Awakened, Mewtwo can breathe in outer space. In the Pokémon Adventures manga, it's revealed Mewtwo's creation wasn't possible with the amount of Mew's cells gathered, so to complete it, human cells was used instead, specifically from the Team Rocket scientist, Blaine. Due to Blaine possessing some of Mewtwo's cells as well, the two became linked, which granted Blaine to ability to track its whereabouts at the cost of slowly taking his life.

Mewtwo is the only known Pokémon capable of learning the move Psystrike.