Cresselia

As one of the bulkiest Pokemon in the entire game, Cresselia stands out as a great defensive and support Pokemon in the tier. Its unparalleled bulk allows it to check a huge variety of threats, including Mega Aerodactyl, Nidoqueen, most Fighting-types, and many more. Its ability, Levitate, grants a useful immunity to Ground attacks, Spikes, and Toxic Spikes, making it even harder to weaken. Cresselia has a great support movepool with access to Thunder Wave, dual screens, Trick Room, and Lunar Dance along with semi-reliable recovery in Moonlight. Despite its fantastic defensive prowess, Cresselia has a mediocre offensive presence and is rather reliant on Calm Mind boosts to deal significant damage. A subpar mono-Psychic typing gives two resistances to Fighting- and Psychic-type attacks but leaves it weak to Dark-, Bug-, and Ghost-type attacks. Finally, Cresselia is very vulnerable to all forms of status and can be easily worn down with burn and poison.