Mew

Mew is one of the best Psychic-types due to its incredible offensive traits and very diverse utility movepool, allowing it to fill the role of a setup threat and bulky stallbreaker. This allows Mew to easily fit on almost any Psychic team due to the number of roles it can fill. Its access to a powerful signature Z-Move in Genesis Supernova in tandem with setup moves such as Nasty Plot and Rock Polish allows Mew to threaten defensive and offensive teams alike while simultaneously offering Psychic Terrain support for the team. Its ability to summon Psychic Terrain is very useful for boosting the power of the team's Psychic-type attacks while also preventing priority users such as Scizor from revenge killing it once weakened. Additionally, Mew's wide support movepool with options such as Taunt, Knock Off, and reliable recovery allows it to serve as an excellent defensive pivot for balance teams, pressuring defensive threats such as Toxapex and Chansey. On top of this, Mew's excellent mixed bulk allows it to check many of the metagame's premier offensive Pokemon such as Kyurem-B and Mega Diancie. Specifically, Mew becomes very difficult to break down specially thanks to its invested bulk, while Will-O-Wisp enables it to check most physical attackers as well, making it extremely hard to check offensively. Mew's unpredictability and versatility further allow it to pressure opposing teams while its set is unrevealed. However, while a pure Psychic typing is decent by itself, it does not add any defensive utility to Psychic teams and instead stacks a common weakness to Dark-, Bug-, and Ghost-types. Mew's power and Speed are quite lacking before setting up and using its Z-Move, so it often finds itself too dependent on setup moves in order to dent teams.