In theory, you can actually sweep with Unown.
Have a Smeargle that knows Quiver Dance, Substitute, Recover, and Baton Pass while holding Leftovers. EVs could probably be Max Sp.D and Def with the rest in Speed/HP. Nature could be Timid/Jolly so that it has a slightly better time when it comes to speed.
The Unown should be holding a Choice Scarf/Choice Specs. It's best to have a Hidden Power type that nothing is immune to (so no Dragon, Ghost, Electric, Normal, Fighting, Ground, or Poison)
The actual strategy: Have Smeargle use Sub first, then spam QD until the sub fades. Use Baton Pass when you think you're comfortable with the stat boost you've accumulated. Then proceed with an embarrassing sweep on your opponent's half.
This strategy is quite easily stopped, so it will take a great deal of luck in order to pull this off. But theoretically, it's possible.
This strategy wont work on most Smogon metas at the time of posting this, since Baton Pass was banned from all tiers except Anything Goes.
Hopefully this helps :)