SOB... specifically Nightmare have deadly enough abilities to win rounds against them
Eadh,, Mawpin, Ghumbo, Oshitsune, Azgroth, Glorg, Phyllis are regulars on the Nightmare deck/half deck that can win rounds using equal or less pills
Piranhas like Tyde and Tula match up well... Smokey and Hawkins can overpill as needed, so that is a decent matchup for Piranhas
Junx also match up quite well. Bangers and UluWatu match up well
but overall, yes All Stars are a well rounded deck that does well vs most decks.... their worst matchup is probably vs a deck that has SOB and attack manipulation
Try out Piranas definitely. Taljion is great versus Robb, Randy and Jessie, while Tyd is strong versus Striker. Smokey Cr and Hawkins are great against Marina and have higher power versus Striker. They can overpill against Robb, Randy and Jessie if needed. Tula owns Robb and Randy but is susceptible to Striker. Use Dalhia for a 5* spot I guess for the power versus all All Stars, but she is a little weak to Randy and Robb.
Nightmare are great too when Oshitsune and/or Ghumbo are unbanned. Use Azgroth to counter Striker, Randy and Jessie, and Oshitsune for Robb, Randy, Marina and Jessie. Pan can go through Marina's DR but Robb has an advantage over him. Ghumbo is great against all AS.
Piranas and Nightmare, as many have said.
I find most of my Piranas decks have very little trouble versus All Stars (draw depending, of course).
Uppers and Rescue counter their -2 in low-mid pill battles.
Montana in mid-high.
Sakrohm, Sentinel, Junkz have bonuses that help too.
Bangers and Ulu Watu cancel out so it becomes a battle of abilities.
Even Skeelz can do well in mono with cards such as Sahsa, Sandro, Chiara, Caelus, Thomas, Danae. And their bonus is completely useless in the context.
It really depends on cards drawn, but every clan has cards that can counter.
The point I'm trying to make is that while some (or most) clans can counter AS, AS can counter all clans. I can't think of a clan that "owns" All Stars.
Let's take Nightmare for example. Robb beats Eadh, Azgroth, Phyllis and Pan. Striker beats Mawpin and Oshitsune. Marina beats Glorg, and her DR is effective against everyone else. And although Ghumbo looks like a good counter, he's 5*, banned most weeks, and becomes significantly less scary if Eyrik is around.
Piranas vs. AS is a bit harder to explain, but to me a significant factor is damage. Most of the Piranas named (Taljion, Tyd, Tula, Smokey Cr, Hawkins) do 4 or fewer damage, which drops to 1 against Marina. Meanwhile, Marina, Striker and Randy deal 5, 6 and 6 each. This means that if the 4 rounds are split 2/2, AS is most likely to win. Are the card-to-card advantages of Piranas enough to win 3 rounds? I'm not so sure.
But I agree that the SOB clans are the most likely solutions. Unfortunately, there are only two of them, and the best cards in both clans are way over my budget at the moment (mumble grumble Smokey mumble grumble).
Then the smart AS players play high pillz against Uppers and Rescue, and low/high pillz against Montana. Combined with their solid damage, AS generally needs to win only 2 of the 4 rounds to win the game. Same with Sakrohm, Sentinel and Junkz. I've had a lot of experience with Montana and Sakrohm (>250 wins each), and I believe AS has the advantage.
Bangers and Ulu Watu do cancel out AS in a head-to-head fight, but on the whole +2 power is weaker than -2 opp. power. It's that whole power ratio thing (math - ick!). And I don't see their abilities as stronger than AS anyway. Advantage: AS.
About Skeelz, I don't understand what you mean by "their bonus is completely useless in the context". All the Skeelz (except Tomas) suffer -2 power, and while Striker is nullified, all the other AS cards are fully functional. Skeelz might have enough cards with high power and good abilities, but I don't think AS is weak against them.
SOA clans are pretty weak against AS I think. They usually have low power and/or damage (other than Shakra, I guess), so the -2 power really hurts.
I've played a lot of La Junta, and they really suffer against AS. Their "natural strong power" is simply not strong enough to handle -2 power (e.g., Wardog and Bruce with their 8 power lose to both Marina and Robb). Even Emeth falls to Striker.
...and I haven't even started complaining about Eyrik yet.