"Pokemon GO" already offers a limited number of pokemon. There are a total of 151 pokemon yet six of them cannot be caught yet. The others are very hard to find, four of them need to be caught all around the world.

The six pokemon not available to catch yet are the three legendary birds, mew, and of course Mewtwo. Mewtwo is known to be one of the most powerful Pokemon in general and overall Pokemon history.

In fact, the only Pokemon believed to be stronger than Mewtwo is Arceus which is the creator of the universe in the Pokemon universe.

That being said, Forbes talks quite a lot about how the introduction to Mewtwo could destroy the entire feel of the game. Why is that?

Well in a normal RPG Pokemon game, if a powerful pokemon is caught it gives the player a massive advantage. Pokemon is a massive MMORPG and so this could lead to total chaos.

If Mewtwo is released, Niantic is sure to do a debut which makes everyone catch their very own Mewtwo or this will cause complains. Once this happens there could be a new wave of millions of Mewtwos spread throughout the Pokemon Go world.

Every single gym could have six or seven Mewtwos and the only way to beat them will be for people to send their own Mewtwos out. 

Mewtwo is the strongest Pokemon of Pokemon Go. According to Ranked Boost it has the highest stats and CP of any pokemon by a longshot. It is the only Pokemon to even cross the 4000 CP barrier. Every other Pokemon, including the legendary birds can only reach 3200 CP at best. 

If this does occur then the over powered legendary may make the usage of all other pokemon completely useless, it could very easily ruin the feel of the game.