If it doesn't do the trick the annihilator 6 will be brutal disruption, it will stop them doing much of much if they survive and it combines with the flying to be pretty effective evasion
Then, you can spend six mana, a kinda steep but not too terrible price, to make a token copy of any artifact you control, except that token is a 1/1 Soldier creature in addition to its other types
Eventually, we found that the answer was to take a creature that we had started in a different color and move it to green, bringing us to Hydras
Even against non-interactive spell decks, Anafenza will end things in a hurry
$5 buy-in, so this may be for more serious competitors
Vampire Hexmage This one is almost always seen with its partner in crime, Dark Depths, to create a 20/20 Marit Lage token, the biggest non-Un-set creature in the game