I sometimes see the term “critical but stable” in the news. It is often used to describe someone who has been very seriously injured.
For example (15 December 2019): "[A police officer] said the man who had been shot was in a "critical but stable " condition in hospital."
I understand that “critically ill” means that life is in danger. Similarly “stable” is the opposite.
Quotes from www.lexico.com
To an extreme degree with a risk of death.
‘two critically wounded people died in hospital’.
‘critically ill patients who were awaiting surgery’
(of a patient or their medical condition) not deteriorating in health after an injury or operation.
‘he is now in a stable condition in hospital’
What does “critical but stable” really mean?