If I have them in deck at the time, Spyke and Fei are pretty good counters.
Or a high-powered Soa like Jackie Cr or Hawk.
Or a decent DR/Defeat: +life like Lola or Clover.
Or just about any half-decent card against Ambre herself. Sure, 9 power with her ability but nobody's gonna pill too much on a 4 damager.
For me, it mostly depends on the level of the player that has Ambre.
If it is a player below level 40, most likely is that he is eager to use his Ambre at 6 pillz, which is a very predictable move, but one against which you can't do much. If it is a more experienced Ambre user, his pillage might be different, but my tactic is the same:
Be a man and take the hit. Send out your hand's DR or SOA if you have one. In most cases, all you can do is take it.
Most people trend to give up the round when Ambre ability is applied.
give up could be DR, SOA, SOB, Defeat: XX, or the most useless card in the hand.
then they fight back the round after that.
My Ambre + Kolos or Karrion face a lot of these situations... Very annoying, but no one want to lose, that's the game.
To br honest with you i find fighting Uppers harder than fighting Ambre. In my experience unless the player using Ambre has a pilz manip or one hit ko, they will usually 3 to 4 pill with Ambre expecting you to one or 2 pill i often pill just enough to beat 4 pilz (usually with copper Hawk or lamar). The next turn do whatever your deck plays to and close. Hope this helped