Capturing Mewtwo is often seen as the pinnacle of Pokemon Red and Blue, adding the arguable strongest Pokemon of all time to the team.
There isn't much to do in Pokemon Red and Blue after battling the Elite Four and becoming the Champion. The biggest objective is to catch Mewtwo.
Once Mewtwo has been caught, it is easy to go back and battle the Elite Four again. Players can also go about completing the Pokedex; doing so with an ultra powerful Mewtwo is an incredible experience.
Note: This article is subjective and reflects the opinion of the writer.
The best moveset for Mewtwo in Pokemon Red and Blue
Mewtwo has a massive Special stat in Generation I. It is also pretty speedy. Amnesia adds on to the great power that the Special stat provides. It raises the Special stat by two stages. In Pokemon Red and Blue, this was the equivalent of both Special Attack and Special Defense.
Blizzard has an accuracy of 90% in Generation I. It also has a 10% chance of freezing the opposing Pokemon. Since battling the Elite Four is really one of the only post-capture activities, Blizzard will handle the Dragon Pokemon of Lance quite well.
Rest keeps the Pokemon using the move healthy. They take a two-turn nap and restore their health to the maximum. This will keep Mewtwo from fainting and will ensure it takes out the entirety of whatever team it faces in the Elite Four. It is a great move in Generation I, but in Gen II it takes three turns to wake up.
Psychic is one of the most powerful moves in Pokemon Red and Blue. It has 100% accuracy and does 90 damage, and also has a 33.2% chance of lowering the opposing Pokemon's Special by one stage. With Psychic as a STAB maneuver along with an insane Special stat, Mewtwo can wreck the Fighting and Poison-type Pokemon of the Elite Four.