To follow up on this:Skarmory is a very good counter being able to Whirlwind it out and taking only around 50% from a +2 ExtremeSpeed with 252HP/0 Def and a Careful nature. As for the second part, I don't know, sorry.
* Scizor can do some good damage with Superpower (~80%).
* Wobbuffet survives a +2 hit and OHKOs with Counter.
* Defensive Mewtwo will always survive a +2 ES and can Will-O-Wisp it.
* Defensive Groudon is never 2HKOd and can stop it with Roar or Toxic.
* Only the Normal SDer can really sweep with ES at +2, so Ghost-types can check it.
@Electro Gypsy: There's always the possibility of Arceus running Thunder to kill Skarmory in the rain.