Nice!
I forgot I had all the pokemon in Excel and just did a search on the text "to each of your opponent's benched pokemon" Found 3 that sounded good:
Garchomp Lv.X Dragon Pulse (Poke Power) - Once during your turn (before your attack), when you put Garchomp Lv. X from your hand onto your Active Garchomp, you may flip 3 coins. For each heads, put 1 damage counter on each of your opponent's Benched Pokemon. (Poke-POWER)
Glaceon Lv.X Avalanche (70, requires 3 energies) Flip a coin. If heads, the attack does 20 damage to each of your opponent's Benched Pokemon. (Don’t apply Weakness and Resistance for Benched Pokemon.)
Ampharos Cluster Bolt (70, requires 3 energies) You may discard all L Energy attached to Ampharos. If you do, this attack does 20 damage to each of your opponent's Benched Pokemon that has any Energy cards attached to it. (Don't apply Weakness and Resistance for Benched Pokemon.)