Duress is covered by the other reply, I think. Imbalance of powers is part of something called "Unconscionability" in the USA. There is an example in the link b

Duress is covered by the other reply, I think. Imbalance of powers is part of something called "Unconscionability" in the USA. There is an example in the link below too. Basically, courts can throw contracts out when they feel they're not fair and that a side with power has taken advantage. I guess that means if you have a heart attack, someone can bill you for cpr, but they can't bill you $100bn for cpr, even if they stand there doing nothing until you "agree". https://en.wikipedia.org/wiki/Unconscionability https://en.wikipedia.org/wiki/Unconscionability