With the introduction of some new cards, there is some debate about what the best card vs SOA, but here is what I think.
#4) Izsobahd: 3 star, Power 8, damage 3, Stop: -3 Pillz Opp. Min 1. With the Vortex ability, this guy is a pain in the pill. Higher damage and he would be rated higher but you can ignore him and eat the 3 damage and 3 pills. If he anticipates this you have a 3 damage and 2-3 pill deficit, but with only 3 damage, its possible to overcome.
3) Glosh: 4 star, Power 6, Damage 6, Stop: Power +3. With the 12 attack from Rescue he is a staple in most rescue decks. A 9/6 with +12 attack vs soa makes him a scary sight. The only issue is that at 4 stars it increases the chances that you go first and he is a bit helpless vs Damage reducers.
2) Karen: 3 Star, Power 7, Damage 4, Stop : - 3 Opp. Life, Min 0. The former king of the anti SOA gang, a scary sight for any Gheist or Roots and will cause a deck with a single SOA to factor their entire game around Karen. Does 5 damage to most damage reducers and causes that scary 7 to 5 power different against most cards where 3-5 pills nets you 7 damage.
1) Flinch: 3 Star, Power 6, Damage 5, Stop : -4 Opp Power, Min 3. That minimum of 3 means that playing 2 pills by Flinch with sentinel +8 attack, makes your standard 7 power opponent play 7 (!!!) pills to beat. 3 stars reduces the chance you have to go first and go up against damage reducers and if your enemy pills high early to avoid him, you can crush them late