I was thinking about this a lot in the last couple of days. As you said, toxicity can be quite different for each people. Some don't even notice it or ignore it because that's just how they handle it. While others are highly sensitive, and it's emotionally hard, frustrating, and demoralizing even to be able to accept it or stand up, and speak out, against it.
I don't think there's a universal measure of toxicity and that's what makes it more difficult to clearly understand and emphatize with each person who went through an experience like that.