Porygon2 is the scariest wallbreaker in the tier. Base 105 Special Attack + the ability to potentially boost that high stat again thanks to Download + a choice specs set leave practically no switchins in this tier. It also has good enough bulk to not fold to strong attacks and will definitely kill its attacker if its attacker fails to beat it. Bulky spdef sets are also incredibly good at handling things like Manectric (you still hate Switcheroo), Victreebel, Altaria and many others.