Absol SW might KO Banette, but if you start with it he won't be able to do much Raiding as Banette outspeeds it. Also, Baleful Wind has a good chance to help the Banette player.
A good counter for Flygon ex d is probably something lame that can withstand 80 damage. I'd personally use Sableye CG, as already suggested. However, 2 Banette SW can actually defeat it if one has a Buffer Piece. Another easier option is Gallade SW, which reduces Flygon ex to 50 HP or 0, depending on how many prizes you plan to open up for it.