Sylveon (F) @ Leftovers
Evs: 252 HP, 4 Sp .Atk, 252 Def
Nature: Bold (+ Def, - Atk)
- Hyper Voice
- Calm Mind
- Heal Bell
Because Sylveon already has superb Sp Def, and has low base Def, it is likely to encounter physical dealers. Invested into Def, Sylveon can take a couple of STAB Earthquakes and various other physical attacks almost equally to its Sp Def capabilities, as long it isn't Steel type.
Special attacks are no threat to Sylveon, as it is very bulky and can stall very well. With Calm Mind, Sylveon can bulk up on Sp Def and reduce any special attacks, whilst, of course, healing with Wish. Sylveon often encounters status dealers, so Heal Bell is used rid those status effects among the whole team. Sylveon goes especially well with a burner or Reflect screener.
Don't underestimate's Sylveon's raw Sp Atk. With +1 Calm Mind, it can wipe out most Dragon types and sweep many unprepared teams with Hyper Voice. It can also go through barriers and Substitute, hence Gliscor and many baton passers can have a hard time dealing with Sylveon.
The one major downside is its Speed. It won't outspeed most Pokemon, hence most opponents will switch out when they find their Pokemon in an unfavorable position against Sylveon. However this works in the favour of Wishing in most scenarios. Also do not go with Dig, as Earthquake will twice as effective, considering its already low speed.