Cresselia

With access to both Trick Room and Magic Coat, Cresselia shines against offensive teams, checking Mega Salamence, Rayquaza, Primal Groudon, Arceus-Ground, Mewtwo, and Deoxys-A thanks to its great 120 / 120 / 130 bulk. Furthermore, Cresselia has access to Lunar Dance, a rare and useful utility move that prevents Cresselia from being total setup bait by letting it get a teammate in healthy. However, Mega Gengar and Steel-type Pokemon give it a very hard time. Balanced and stall teams, which don't care about Trick Room, run many Pokemon that wall Cresselia. It also lacks a phazing move, which makes it setup bait for any Pokemon running Aromatherapy, Substitute, or Refresh. Finally, Cresselia faces steep competition with Lugia, especially with regards to defensive duties.