Articuno @ Leftovers@ace15's Swampert
Tangrowth @ Lefties
Resists Waterfall, shrugs off all other damage and hits back with Energy Ball, which will OHKO.
This can come in on either of your attacks as they both hit NVE. Outspeeds Tangrowth by plenty and sets up a Substitute and fires off Super Effective STAB Ice Beams.